diff --git a/lib/mix/lib/mix/project.ex b/lib/mix/lib/mix/project.ex
index d7ae332754d..ec10da1d000 100644
--- a/lib/mix/lib/mix/project.ex
+++ b/lib/mix/lib/mix/project.ex
@@ -899,6 +899,20 @@ defmodule Mix.Project do
     Mix.Lock.with_lock(build_path, fun, on_taken: on_taken)
   end
 
+  @doc false
+  def with_deps_lock(config \\ config(), fun) do
+    # We wrap operations on the deps directory and on mix.lock to
+    # avoid write conflicts.
+
+    deps_path = deps_path(config)
+
+    on_taken = fn os_pid ->
+      Mix.shell().info("Waiting for lock on the deps directory (held by process #{os_pid})")
+    end
+
+    Mix.Lock.with_lock(deps_path, fun, on_taken: on_taken)
+  end
+
   # Loads mix.exs in the current directory or loads the project from the
   # mixfile cache and pushes the project onto the project stack.
   defp load_project(app, post_config) do
diff --git a/lib/mix/lib/mix/tasks/clean.ex b/lib/mix/lib/mix/tasks/clean.ex
index a51b235a343..18c01dd1685 100644
--- a/lib/mix/lib/mix/tasks/clean.ex
+++ b/lib/mix/lib/mix/tasks/clean.ex
@@ -30,6 +30,12 @@ defmodule Mix.Tasks.Clean do
 
     {opts, _, _} = OptionParser.parse(args, switches: @switches)
 
+    Mix.Project.with_build_lock(fn ->
+      do_run(opts)
+    end)
+  end
+
+  defp do_run(opts) do
     # First, we get the tasks. After that, we clean them.
     # This is to avoid a task cleaning a compiler module.
     tasks =
diff --git a/lib/mix/lib/mix/tasks/deps.clean.ex b/lib/mix/lib/mix/tasks/deps.clean.ex
index ef40731d330..93279343a79 100644
--- a/lib/mix/lib/mix/tasks/deps.clean.ex
+++ b/lib/mix/lib/mix/tasks/deps.clean.ex
@@ -63,13 +63,19 @@ defmodule Mix.Tasks.Deps.Clean do
           )
       end
 
-    do_clean(apps_to_clean, loaded_deps, build_path, deps_path, opts[:build])
+    Mix.Project.with_build_lock(fn ->
+      clean_build(apps_to_clean, build_path)
+    end)
 
-    if opts[:unlock] do
-      Mix.Task.run("deps.unlock", args)
-    else
-      :ok
-    end
+    Mix.Project.with_deps_lock(fn ->
+      clean_source(apps_to_clean, loaded_deps, deps_path, opts[:build])
+
+      if opts[:unlock] do
+        Mix.Task.run("deps.unlock", args)
+      else
+        :ok
+      end
+    end)
   end
 
   defp checked_deps(build_path, deps_path) do
@@ -108,11 +114,9 @@ defmodule Mix.Tasks.Deps.Clean do
     end
   end
 
-  defp do_clean(apps, deps, build_path, deps_path, build_only?) do
+  defp clean_build(apps, build_path) do
     shell = Mix.shell()
 
-    local = for %{scm: scm, app: app} <- deps, not scm.fetchable?(), do: Atom.to_string(app)
-
     Enum.each(apps, fn app ->
       shell.info("* Cleaning #{app}")
 
@@ -122,7 +126,13 @@ defmodule Mix.Tasks.Deps.Clean do
       |> Path.wildcard()
       |> maybe_warn_for_invalid_path(app)
       |> Enum.map(&(&1 |> File.rm_rf() |> maybe_warn_failed_file_deletion()))
+    end)
+  end
 
+  defp clean_source(apps, deps, deps_path, build_only?) do
+    local = for %{scm: scm, app: app} <- deps, not scm.fetchable?(), do: Atom.to_string(app)
+
+    Enum.each(apps, fn app ->
       # Remove everything from the source directory of dependencies.
       # Skip this step if --build option is specified or if
       # the dependency is local, i.e., referenced using :path.
diff --git a/lib/mix/lib/mix/tasks/deps.get.ex b/lib/mix/lib/mix/tasks/deps.get.ex
index 4e63c218bea..12fae37aec2 100644
--- a/lib/mix/lib/mix/tasks/deps.get.ex
+++ b/lib/mix/lib/mix/tasks/deps.get.ex
@@ -26,6 +26,12 @@ defmodule Mix.Tasks.Deps.Get do
     {opts, _, _} =
       OptionParser.parse(args, switches: [only: :string, target: :string, check_locked: :boolean])
 
+    Mix.Project.with_deps_lock(fn ->
+      do_run(opts)
+    end)
+  end
+
+  defp do_run(opts) do
     fetch_opts =
       for {switch, key} <- [only: :env, target: :target, check_locked: :check_locked],
           value = opts[switch],
diff --git a/lib/mix/lib/mix/tasks/deps.unlock.ex b/lib/mix/lib/mix/tasks/deps.unlock.ex
index eb72786254c..27c5d8d6059 100644
--- a/lib/mix/lib/mix/tasks/deps.unlock.ex
+++ b/lib/mix/lib/mix/tasks/deps.unlock.ex
@@ -27,6 +27,12 @@ defmodule Mix.Tasks.Deps.Unlock do
     Mix.Project.get!()
     {opts, apps, _} = OptionParser.parse(args, switches: @switches)
 
+    Mix.Project.with_deps_lock(fn ->
+      do_run(opts, apps)
+    end)
+  end
+
+  defp do_run(opts, apps) do
     cond do
       opts[:all] ->
         Mix.Dep.Lock.write(%{})
diff --git a/lib/mix/lib/mix/tasks/deps.update.ex b/lib/mix/lib/mix/tasks/deps.update.ex
index d74a0b105c3..529dad817f3 100644
--- a/lib/mix/lib/mix/tasks/deps.update.ex
+++ b/lib/mix/lib/mix/tasks/deps.update.ex
@@ -45,6 +45,12 @@ defmodule Mix.Tasks.Deps.Update do
     {opts, rest, _} =
       OptionParser.parse(args, switches: [all: :boolean, only: :string, target: :string])
 
+    Mix.Project.with_deps_lock(fn ->
+      do_run(opts, rest)
+    end)
+  end
+
+  defp do_run(opts, rest) do
     fetch_opts =
       for {switch, key} <- [only: :env, target: :target],
           value = opts[switch],