diff --git a/CHANGELOG.md b/CHANGELOG.md
index 34c5966..93cfd12 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@
   assert expectations
 - refactor code that sets 'TMUX_PLUGIN_MANAGER_PATH' global env var
 - stop using global variable for 'tpm path'
+- support defining plugins via `set -g @plugin` in sourced files as well
 
 ### v2.0.0, 2015-07-07
 - enable overriding default key bindings
diff --git a/scripts/helpers/plugin_functions.sh b/scripts/helpers/plugin_functions.sh
index 4c34412..e1da249 100644
--- a/scripts/helpers/plugin_functions.sh
+++ b/scripts/helpers/plugin_functions.sh
@@ -1,21 +1,40 @@
 # using @tpm_plugins is now deprecated in favor of using @plugin syntax
 tpm_plugins_variable_name="@tpm_plugins"
 
+# manually expanding tilde char or `$HOME` variable.
+_manual_expansion() {
+	local path="$1"
+	local expanded_tilde="${path/#\~/$HOME}"
+	echo "${expanded_tilde/#\$HOME/$HOME}"
+}
+
 _tpm_path() {
 	local string_path="$(tmux start-server\; show-environment -g TMUX_PLUGIN_MANAGER_PATH | cut -f2 -d=)/"
-	# manually expanding tilde or `$HOME` variable.
-	string_path="${string_path/#\~/$HOME}"
-	echo "${string_path/#\$HOME/$HOME}"
+	_manual_expansion "$string_path"
 }
 
 _CACHED_TPM_PATH="$(_tpm_path)"
 
-tpm_path() {
-	echo "$_CACHED_TPM_PATH"
-}
-
 _tmux_conf_contents() {
 	cat /etc/tmux.conf ~/.tmux.conf 2>/dev/null
+	if [ "$1" == "full" ]; then # also output content from sourced files
+		local file
+		for file in $(_sourced_files); do
+			cat $(_manual_expansion "$file") 2>/dev/null
+		done
+	fi
+}
+
+# return files sourced from tmux config files
+_sourced_files() {
+	_tmux_conf_contents |
+		awk '/^ *source(-file)? +/ { gsub(/'\''/,""); gsub(/'\"'/,""); print $2 }'
+}
+
+# PUBLIC FUNCTIONS BELOW
+
+tpm_path() {
+	echo "$_CACHED_TPM_PATH"
 }
 
 tpm_plugins_list_helper() {
@@ -23,7 +42,7 @@ tpm_plugins_list_helper() {
 	echo "$(tmux start-server\; show-option -gqv "$tpm_plugins_variable_name")"
 
 	# read set -g @plugin "tmux-plugins/tmux-example-plugin" entries
-	_tmux_conf_contents |
+	_tmux_conf_contents "full" |
 		awk '/^ *set +-g +@plugin/ { gsub(/'\''/,""); gsub(/'\"'/,""); print $4 }'
 }
 
diff --git a/tests/test_plugin_installation.sh b/tests/test_plugin_installation.sh
index c161746..7e3404d 100755
--- a/tests/test_plugin_installation.sh
+++ b/tests/test_plugin_installation.sh
@@ -5,6 +5,8 @@ PLUGINS_DIR="$HOME/.tmux/plugins"
 TPM_DIR="$PWD"
 
 CUSTOM_PLUGINS_DIR="$HOME/foo/plugins"
+ADDITIONAL_CONFIG_FILE_1="$HOME/.tmux/additional_config_file_1"
+ADDITIONAL_CONFIG_FILE_2="$HOME/.tmux/additional_config_file_2"
 
 source "$CURRENT_DIR/helpers/helpers.sh"
 source "$CURRENT_DIR/helpers/tpm.sh"
@@ -63,7 +65,6 @@ test_multiple_plugins_installation_via_tmux_key_binding() {
 	run-shell "$TPM_DIR/tpm"
 	HERE
 
-	# opens tmux and test it with `expect`
 	"$CURRENT_DIR/expect_successful_multiple_plugins_download" ||
 		fail_helper "[key-binding] multiple plugins installation fails"
 
@@ -76,6 +77,51 @@ test_multiple_plugins_installation_via_tmux_key_binding() {
 	teardown_helper
 }
 
+test_plugins_installation_from_sourced_file_via_tmux_key_binding() {
+	set_tmux_conf_helper <<- HERE
+	source '$ADDITIONAL_CONFIG_FILE_1'
+	set -g @plugin 'tmux-plugins/tmux-example-plugin'
+	run-shell "$TPM_DIR/tpm"
+	HERE
+
+	mkdir ~/.tmux
+	echo "set -g @plugin 'tmux-plugins/tmux-copycat'" > "$ADDITIONAL_CONFIG_FILE_1"
+
+	"$CURRENT_DIR/expect_successful_multiple_plugins_download" ||
+		fail_helper "[key-binding][sourced file] plugins installation fails"
+
+	check_dir_exists_helper "$PLUGINS_DIR/tmux-example-plugin/" ||
+		fail_helper "[key-binding][sourced file] plugin download fails (tmux-example-plugin)"
+
+	check_dir_exists_helper "$PLUGINS_DIR/tmux-copycat/" ||
+		fail_helper "[key-binding][sourced file] plugin download fails (tmux-copycat)"
+
+	teardown_helper
+}
+
+test_plugins_installation_from_multiple_sourced_files_via_tmux_key_binding() {
+	set_tmux_conf_helper <<- HERE
+	\ \ source    '$ADDITIONAL_CONFIG_FILE_1'
+	source-file '$ADDITIONAL_CONFIG_FILE_2'
+	run-shell "$TPM_DIR/tpm"
+	HERE
+
+	mkdir ~/.tmux
+	echo "set -g @plugin 'tmux-plugins/tmux-example-plugin'" > "$ADDITIONAL_CONFIG_FILE_1"
+	echo "  set -g @plugin 'tmux-plugins/tmux-copycat'" > "$ADDITIONAL_CONFIG_FILE_2"
+
+	"$CURRENT_DIR/expect_successful_multiple_plugins_download" ||
+		fail_helper "[key-binding][multiple sourced files] plugins installation fails"
+
+	check_dir_exists_helper "$PLUGINS_DIR/tmux-example-plugin/" ||
+		fail_helper "[key-binding][multiple sourced files] plugin download fails (tmux-example-plugin)"
+
+	check_dir_exists_helper "$PLUGINS_DIR/tmux-copycat/" ||
+		fail_helper "[key-binding][multiple sourced files] plugin download fails (tmux-copycat)"
+
+	teardown_helper
+}
+
 # SCRIPT TESTS
 
 test_plugin_installation_via_script() {
@@ -152,4 +198,59 @@ test_multiple_plugins_installation_via_script() {
 	teardown_helper
 }
 
+test_plugins_installation_from_sourced_file_via_script() {
+	set_tmux_conf_helper <<- HERE
+	source '$ADDITIONAL_CONFIG_FILE_1'
+	set -g @plugin 'tmux-plugins/tmux-example-plugin'
+	run-shell "$TPM_DIR/tpm"
+	HERE
+
+	mkdir ~/.tmux
+	echo "set -g @plugin 'tmux-plugins/tmux-copycat'" > "$ADDITIONAL_CONFIG_FILE_1"
+
+	script_run_helper "$TPM_DIR/bin/install_plugins" '"tmux-copycat" download success' ||
+		fail_helper "[script][sourced file] plugins installation fails"
+
+	check_dir_exists_helper "$PLUGINS_DIR/tmux-example-plugin/" ||
+		fail_helper "[script][sourced file] plugin download fails (tmux-example-plugin)"
+
+	check_dir_exists_helper "$PLUGINS_DIR/tmux-copycat/" ||
+		fail_helper "[script][sourced file] plugin download fails (tmux-copycat)"
+
+	script_run_helper "$TPM_DIR/bin/install_plugins" 'Already installed "tmux-copycat"' ||
+		fail_helper "[script][sourced file] plugins already installed message fail"
+
+	teardown_helper
+}
+
+test_plugins_installation_from_multiple_sourced_files_via_script() {
+	set_tmux_conf_helper <<- HERE
+	\ \ source    '$ADDITIONAL_CONFIG_FILE_1'
+	source-file '$ADDITIONAL_CONFIG_FILE_2'
+	set -g @plugin 'tmux-plugins/tmux-example-plugin'
+	run-shell "$TPM_DIR/tpm"
+	HERE
+
+	mkdir ~/.tmux
+	echo " set   -g @plugin 'tmux-plugins/tmux-copycat'" > "$ADDITIONAL_CONFIG_FILE_1"
+	echo "set -g @plugin 'tmux-plugins/tmux-sensible'" > "$ADDITIONAL_CONFIG_FILE_2"
+
+	script_run_helper "$TPM_DIR/bin/install_plugins" '"tmux-sensible" download success' ||
+		fail_helper "[script][multiple sourced files] plugins installation fails"
+
+	check_dir_exists_helper "$PLUGINS_DIR/tmux-example-plugin/" ||
+		fail_helper "[script][multiple sourced files] plugin download fails (tmux-example-plugin)"
+
+	check_dir_exists_helper "$PLUGINS_DIR/tmux-copycat/" ||
+		fail_helper "[script][multiple sourced files] plugin download fails (tmux-copycat)"
+
+	check_dir_exists_helper "$PLUGINS_DIR/tmux-sensible/" ||
+		fail_helper "[script][multiple sourced files] plugin download fails (tmux-sensible)"
+
+	script_run_helper "$TPM_DIR/bin/install_plugins" 'Already installed "tmux-sensible"' ||
+		fail_helper "[script][multiple sourced files] plugins already installed message fail"
+
+	teardown_helper
+}
+
 run_tests