diff --git a/NEWS.md b/NEWS.md
index c7a64c04e..25cefd9c0 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -7,6 +7,8 @@ plumber 1.0.0.9999 Development version
 
 * When plumbing a Plumber file and using a Plumber router modifier (`#* @plumber`), an error will be thrown if the original router is not returned. (#738)
 
+* When processing a route, the mount location with the larger path match will be used. Before, the first mount added that could possibly process the requested path was used. For more details, see `?pr_mount`. (#748)
+
 ### New features
 
 * Guess OpenApi response content type from serializer. (@meztez #684)
diff --git a/R/default-handlers.R b/R/default-handlers.R
index 8784c36c3..02d31bb64 100644
--- a/R/default-handlers.R
+++ b/R/default-handlers.R
@@ -42,7 +42,7 @@ defaultErrorHandler <- function(){
 #' @noRd
 allowed_verbs <- function(pr, path_to_find) {
 
-  verbs_allowed <- c()
+  verbs_allowed <- NULL
 
   # look at all possible endpoints
   for (endpoint_group in pr$endpoints) {
@@ -54,9 +54,10 @@ allowed_verbs <- function(pr, path_to_find) {
   }
 
   # look at all possible mounts
-  for (i in seq_along(pr$mounts)) {
-    mount <- pr$mounts[[i]]
-    mount_path <- sub("/$", "", names(pr$mounts)[i]) # trim trailing `/`
+  mnts <- pr$mounts
+  for (i in seq_along(mnts)) {
+    mount <- mnts[[i]]
+    mount_path <- sub("/$", "", names(mnts)[i]) # trim trailing `/`
 
     # if the front of the urls don't match, move on to next mount
     if (!identical(
@@ -77,6 +78,9 @@ allowed_verbs <- function(pr, path_to_find) {
   }
 
   # return verbs
+  if (is.null(verbs_allowed)) {
+    return(verbs_allowed)
+  }
   sort(unique(verbs_allowed))
 }
 
diff --git a/R/openapi-spec.R b/R/openapi-spec.R
index 7dce8466f..dfa9a1cd5 100644
--- a/R/openapi-spec.R
+++ b/R/openapi-spec.R
@@ -210,7 +210,7 @@ isNa <- function(x) {
 #' Check na or null
 #' @noRd
 isNaOrNull <- function(x) {
-  any(isNa(x)) || is.null(x)
+  is.null(x) || any(isNa(x))
 }
 
 #' Remove na or null
diff --git a/R/openapi-types.R b/R/openapi-types.R
index 45a558e9f..a966078fe 100644
--- a/R/openapi-types.R
+++ b/R/openapi-types.R
@@ -92,7 +92,7 @@ plumberToApiType <- function(type, inPath = FALSE) {
     return(vapply(type, plumberToApiType, character(1), inPath, USE.NAMES = FALSE))
   }
   # default type is "string" type
-  if (is.na(type)) {
+  if (isNaOrNull(type)) {
     return(defaultApiType)
   }
 
diff --git a/R/plumber.R b/R/plumber.R
index e30cefedf..1637d0247 100644
--- a/R/plumber.R
+++ b/R/plumber.R
@@ -220,6 +220,12 @@ Plumber <- R6Class(
     #' using the `mount()` method. This allows you to compartmentalize your API
     #' by paths which is a great technique for decomposing large APIs into smaller files.
     #'
+    #' Mounts with a more specific path name will be used over mounts with a
+    #' matching, but less specific path name. For example, let's say we have two
+    #' mounts: `/aaa` and `/aaa/bbb`. If a request came in for `/aaa/bbb/ccc`,
+    #' mount `/aaa/bbb` will be used to process the request. If a request came in
+    #' for `/aaa/ccc`, mount `/aaa` will be used to process the request.
+    #'
     #' See also: [pr_mount()]
     #' @param path a character string. Where to mount router.
     #' @param router a Plumber router. Router to be mounted.
@@ -242,7 +248,9 @@ Plumber <- R6Class(
         path <- paste0(path, "/")
       }
 
+      # order the mounts so that the more specific mount paths are ahead of the less specific mount paths
       private$mnts[[path]] <- router
+      private$mnts <- private$mnts[order(names(private$mnts), decreasing = TRUE)]
     },
     #' @description Unmount a Plumber router
     #' @param path a character string. Where to unmount router.
@@ -410,7 +418,7 @@ Plumber <- R6Class(
 
       cat(crayon::silver("# Plumber router with ", endCount, " endpoint", ifelse(endCount == 1, "", "s"),", ",
                          as.character(length(private$filts)), " filter", ifelse(length(private$filts) == 1, "", "s"),", and ",
-                         as.character(length(self$mounts)), " sub-router", ifelse(length(self$mounts) == 1, "", "s"),".\n", sep=""))
+                         as.character(length(private$mnts)), " sub-router", ifelse(length(private$mnts) == 1, "", "s"),".\n", sep=""))
 
       if(topLevel){
         cat(prefix, crayon::silver("# Use `pr_run()` on this object to start the API.\n"), sep="")
@@ -704,8 +712,18 @@ Plumber <- R6Class(
       # If we still haven't found a match, check the un-preempt'd endpoints.
       steps <- append(steps, list(makeHandleStep("__no-preempt__")))
 
-      # We aren't going to serve this endpoint; see if any mounted routers will
-      mountSteps <- lapply(names(private$mnts), function(mountPath) {
+      # This router can not serve this endpoint; See if any mounted routers will.
+      # `private$mnts` is reverse alpha-sorted to have more specific mount paths be found first.
+      # `self$mounts` is alpha-sorted to have less specific mount paths be found first.
+      # Ex:
+      # * `/aaa/bbb/foo` is requested.
+      # * Mounts `/aaa` and `/aaa/bbb` exist.
+      # * We want to use mount `/aaa/bbb` as it is more specific
+      # TODO
+      # * If `/aaa/bbb` mount does not support `/aaa/bbb/foo`, then try mount `/aaa`.
+      # * Current behavior is to return a 404
+      mnts <- private$mnts
+      mountSteps <- lapply(names(mnts), function(mountPath) {
         # (make step function)
         function(...) {
           resetForward()
@@ -716,7 +734,7 @@ Plumber <- R6Class(
 
             # First trim the prefix off of the PATH_INFO element
             req$PATH_INFO <- substr(req$PATH_INFO, nchar(mountPath), nchar(req$PATH_INFO))
-            return(private$mnts[[mountPath]]$route(req, res))
+            return(mnts[[mountPath]]$route(req, res))
           } else {
             return(forward())
           }
@@ -935,7 +953,7 @@ Plumber <- R6Class(
       private$api_spec_handler <- api_fun
     },
     #' @description Retrieve openAPI file
-    getApiSpec = function() { #FIXME: test
+    getApiSpec = function() {
 
       routerSpec <- private$routerSpecificationInternal(self)
 
@@ -1021,23 +1039,25 @@ Plumber <- R6Class(
       self$getApiSpec()
     }
   ), active = list(
-    #' @field endpoints Plumber router endpoints read-only
+    #' @field endpoints Plumber router endpoints. Read-only
     endpoints = function(){
       private$ends
     },
-    #' @field filters Plumber router filters read-only
+    #' @field filters Plumber router filters. Read-only
     filters = function(){
       private$filts
     },
-    #' @field mounts Plumber router mounts read-only
+    #' @field mounts Plumber router mounts sorted by mount location. Read-only.
     mounts = function(){
-      private$mnts
+      mnts <- private$mnts
+      if (length(mnts) == 0) return(mnts)
+      mnts[sort(names(mnts), decreasing = FALSE)]
     },
-    #' @field environment Plumber router environment read-only
+    #' @field environment Plumber router environment. Read-only
     environment = function() {
       private$envir
     },
-    #' @field routes Plumber router routes read-only
+    #' @field routes Plumber router routes. Read-only
     routes = function(){
       paths <- list()
 
@@ -1057,7 +1077,8 @@ Plumber <- R6Class(
 
         # Check for existing endpoints at current children node that share the same name
         matching_name_nodes <- node[names(node) == children[1]]
-        existing_endpoints <- vapply(matching_name_nodes, inherits, logical(1), "PlumberEndpoint")
+        # if there is an endpoint or router...
+        existing_endpoints <- vapply(matching_name_nodes, inherits, logical(1), c("PlumberEndpoint", "Plumber"))
 
         # This is for situation where an endpoint is on `/A` and you
         # also have route with an endpoint on `A/B`. Resulting nested list
@@ -1091,16 +1112,16 @@ Plumber <- R6Class(
       })
 
       # Sub-routers
-      if (length(self$mounts) > 0){
-        for(i in 1:length(self$mounts)){
+      mnts <- self$mounts
+      if (length(mnts) > 0) {
+        Map(mnts, names(mnts), f = function(mnt, mnt_name) {
           # Trim leading slash
-          path <- sub("^/", "", names(self$mounts)[i])
+          path <- sub("^/", "", mnt_name)
 
           levels <- strsplit(path, "/", fixed=TRUE)[[1]]
 
-          m <- self$mounts[[i]]
-          paths <- addPath(paths, levels, m)
-        }
+          paths <<- addPath(paths, levels, mnt)
+        })
       }
 
       lexisort <- function(paths) {
@@ -1211,10 +1232,11 @@ Plumber <- R6Class(
       }
 
       # recursively gather mounted enpoint entries
-      if (length(router$mounts) > 0) {
-        for (mountPath in names(router$mounts)) {
+      router_mnts <- router$mounts
+      if (length(router_mnts) > 0) {
+        for (mountPath in sort(names(router_mnts))) {
           mountEndpoints <- private$routerSpecificationInternal(
-            router$mounts[[mountPath]],
+            router_mnts[[mountPath]],
             join_paths(parentPath, mountPath)
           )
           endpointList <- utils::modifyList(endpointList, mountEndpoints)
diff --git a/R/pr.R b/R/pr.R
index ec2c4219e..71363171d 100644
--- a/R/pr.R
+++ b/R/pr.R
@@ -209,6 +209,12 @@ pr_head <- function(pr,
 #' files. This function mutates the Plumber router ([pr()]) in place and
 #' returns the updated router.
 #'
+#' Mounts with a more specific path name will be used over mounts with a
+#' matching, but less specific path name. For example, let's say we have two
+#' mounts: `/aaa` and `/aaa/bbb`. If a request came in for `/aaa/bbb/ccc`,
+#' mount `/aaa/bbb` will be used to process the request. If a request came in
+#' for `/aaa/ccc`, mount `/aaa` will be used to process the request.
+#'
 #' @param pr The host Plumber router.
 #' @param path A character string. Where to mount router.
 #' @param router A Plumber router. Router to be mounted.
@@ -222,6 +228,7 @@ pr_head <- function(pr,
 #'
 #' pr() %>%
 #'   pr_get("/goodbye", function() "Goodbye") %>%
+#'   # By mounting pr1, we can make a GET request to `/hi/hello`
 #'   pr_mount("/hi", pr1) %>%
 #'   pr_run()
 #' }
diff --git a/man/Plumber.Rd b/man/Plumber.Rd
index 11736bc4e..f126a5fdf 100644
--- a/man/Plumber.Rd
+++ b/man/Plumber.Rd
@@ -126,15 +126,15 @@ pr$setErrorHandler(function(req, res, err) {
 \section{Active bindings}{
 \if{html}{\out{<div class="r6-active-bindings">}}
 \describe{
-\item{\code{endpoints}}{Plumber router endpoints read-only}
+\item{\code{endpoints}}{Plumber router endpoints. Read-only}
 
-\item{\code{filters}}{Plumber router filters read-only}
+\item{\code{filters}}{Plumber router filters. Read-only}
 
-\item{\code{mounts}}{Plumber router mounts read-only}
+\item{\code{mounts}}{Plumber router mounts sorted by mount location. Read-only.}
 
-\item{\code{environment}}{Plumber router environment read-only}
+\item{\code{environment}}{Plumber router environment. Read-only}
 
-\item{\code{routes}}{Plumber router routes read-only}
+\item{\code{routes}}{Plumber router routes. Read-only}
 }
 \if{html}{\out{</div>}}
 }
@@ -256,6 +256,12 @@ Plumber routers can be “nested” by mounting one into another
 using the \code{mount()} method. This allows you to compartmentalize your API
 by paths which is a great technique for decomposing large APIs into smaller files.
 
+Mounts with a more specific path name will be used over mounts with a
+matching, but less specific path name. For example, let's say we have two
+mounts: \verb{/aaa} and \verb{/aaa/bbb}. If a request came in for \verb{/aaa/bbb/ccc},
+mount \verb{/aaa/bbb} will be used to process the request. If a request came in
+for \verb{/aaa/ccc}, mount \verb{/aaa} will be used to process the request.
+
 See also: \code{\link[=pr_mount]{pr_mount()}}
 \subsection{Usage}{
 \if{html}{\out{<div class="r">}}\preformatted{Plumber$mount(path, router)}\if{html}{\out{</div>}}
diff --git a/man/pr_mount.Rd b/man/pr_mount.Rd
index 7f08d1c13..cacb7ab7a 100644
--- a/man/pr_mount.Rd
+++ b/man/pr_mount.Rd
@@ -23,6 +23,13 @@ by paths which is a great technique for decomposing large APIs into smaller
 files. This function mutates the Plumber router (\code{\link[=pr]{pr()}}) in place and
 returns the updated router.
 }
+\details{
+Mounts with a more specific path name will be used over mounts with a
+matching, but less specific path name. For example, let's say we have two
+mounts: \verb{/aaa} and \verb{/aaa/bbb}. If a request came in for \verb{/aaa/bbb/ccc},
+mount \verb{/aaa/bbb} will be used to process the request. If a request came in
+for \verb{/aaa/ccc}, mount \verb{/aaa} will be used to process the request.
+}
 \examples{
 \dontrun{
 pr1 <- pr() \%>\%
@@ -30,6 +37,7 @@ pr1 <- pr() \%>\%
 
 pr() \%>\%
   pr_get("/goodbye", function() "Goodbye") \%>\%
+  # By mounting pr1, we can make a GET request to `/hi/hello`
   pr_mount("/hi", pr1) \%>\%
   pr_run()
 }
diff --git a/tests/testthat/test-routing.R b/tests/testthat/test-routing.R
index 224d08451..a3a4d4620 100644
--- a/tests/testthat/test-routing.R
+++ b/tests/testthat/test-routing.R
@@ -33,3 +33,38 @@ test_that("Routing to errors and 404s works", {
   expect_equal(er, errRes)
   expect_equal(errors, 1)
 })
+
+
+test_that("mounts with more specific paths are used", {
+
+  root <- pr() %>%
+    pr_mount("/aaa",
+      pr() %>%
+        pr_get("/bbb/hello", function() "/aaa - /bbb/hello") %>%
+        pr_get("/bbb/test", function() "/aaa - /bbb/test")
+    ) %>%
+    pr_mount("/aaa/bbb",
+      pr() %>%
+        pr_get("/hello", function() "/aaa/bbb - /hello") %>%
+        pr_set_404(function(...) { "404" })
+    )
+
+
+  # make sure it can print without error... which calls root$routes
+  expect_error(capture.output(print(root)), NA)
+
+  res <- PlumberResponse$new()
+  # route with more specific mount is used
+  expect_equal(
+    root$route(make_req("GET", "/aaa/bbb/hello"), res),
+    "/aaa/bbb - /hello"
+  )
+
+  # currently "bad" behavior. TODO - make this return "/aaa - /bbb/test"
+  expect_equal(
+    root$route(make_req("GET", "/aaa/bbb/test"), res),
+    "404"
+  )
+
+
+})