diff --git a/R/filter_by_agency_id.R b/R/filter_by_agency_id.R
index b462b76..c6ecbaa 100644
--- a/R/filter_by_agency_id.R
+++ b/R/filter_by_agency_id.R
@@ -63,8 +63,9 @@ filter_by_agency_id <- function(gtfs, agency_id, keep = TRUE) {
 
   relevant_routes <- unique(gtfs$routes$route_id)
 
-  # 'fare_rules' and 'trips' (route_id)
+  # 'fare_rules', 'trips' and 'transfers' (route_id)
 
+  gtfs <- filter_transfers_from_route_id(gtfs, relevant_routes, `%chin%`)
   gtfs <- filter_fare_rules_from_route_id(gtfs, relevant_routes, `%chin%`)
   gtfs <- filter_trips_from_route_id(gtfs, relevant_routes, `%chin%`)
 
@@ -83,8 +84,9 @@ filter_by_agency_id <- function(gtfs, agency_id, keep = TRUE) {
   gtfs <- filter_calendar_from_service_id(gtfs, relevant_services, `%chin%`)
   gtfs <- filter_calend_dates_from_service_id(gtfs, relevant_services, `%chin%`)
 
-  # 'stop_times' and 'frequencies' (trip_id)
+  # 'stop_times', 'frequencies' and 'transfers' (trip_id)
 
+  gtfs <- filter_transfers_from_trip_id(gtfs, relevant_trips, `%chin%`)
   gtfs <- filter_frequencies_from_trip_id(gtfs, relevant_trips, `%chin%`)
   gtfs <- filter_stop_times_from_trip_id(gtfs, relevant_trips, `%chin%`)
 
diff --git a/R/filter_by_shape_id.R b/R/filter_by_shape_id.R
index a363027..b2382ec 100644
--- a/R/filter_by_shape_id.R
+++ b/R/filter_by_shape_id.R
@@ -61,7 +61,7 @@ filter_by_shape_id <- function(gtfs, shape_id, keep = TRUE) {
   gtfs <- filter_calendar_from_service_id(gtfs, relevant_services, `%chin%`)
   gtfs <- filter_calend_dates_from_service_id(gtfs, relevant_services, `%chin%`)
 
-  # 'routes' and 'fare_rules' (route_id)
+  # 'routes', 'fare_rules' and 'transfers' (route_id)
   #
   # we can use 'routes' to filter agency via routes -> agency_id, but we can
   # also use 'fare_rules' to filter it via fare_rules -> fare_id ->
@@ -69,6 +69,7 @@ filter_by_shape_id <- function(gtfs, shape_id, keep = TRUE) {
   # so we create a 'relevant_agencies' vector that holds the relevant
   # agency_ids from both paths and use all of them to filter agency later.
 
+  gtfs <- filter_transfers_from_route_id(gtfs, relevant_routes, `%chin%`)
   gtfs <- filter_routes_from_route_id(gtfs, relevant_routes, `%chin%`)
   gtfs <- filter_fare_rules_from_route_id(gtfs, relevant_routes, `%chin%`)
   relevant_agencies_from_routes <- unique(gtfs$routes$agency_id)
@@ -92,8 +93,9 @@ filter_by_shape_id <- function(gtfs, shape_id, keep = TRUE) {
 
   gtfs <- filter_agency_from_agency_id(gtfs, relevant_agencies, `%chin%`)
 
-  # 'stop_times' and 'frequencies' (trip_id)
+  # 'stop_times', 'frequencies' and 'transfers' (trip_id)
 
+  gtfs <- filter_transfers_from_trip_id(gtfs, relevant_trips, `%chin%`)
   gtfs <- filter_frequencies_from_trip_id(gtfs, relevant_trips, `%chin%`)
   gtfs <- filter_stop_times_from_trip_id(gtfs, relevant_trips, `%chin%`)
 
diff --git a/R/filter_by_trip_id.R b/R/filter_by_trip_id.R
index 263b892..38a7183 100644
--- a/R/filter_by_trip_id.R
+++ b/R/filter_by_trip_id.R
@@ -38,9 +38,10 @@ filter_by_trip_id <- function(gtfs, trip_id, keep = TRUE) {
   `%ffilter%` <- `%chin%`
   if (!keep) `%ffilter%` <- Negate(`%chin%`)
 
-  # 'trips', 'stop_times' and 'frequencies' can be filtered using 'trip_id'
-  # itself, so `%ffilter%` is used. the other files depend on relational
-  # associations with 'trip_id' that come from these 3 tables, so we use %chin%
+  # 'trips', 'stop_times', 'frequencies' and 'transfers' can be filtered using
+  # 'trip_id' itself, so `%ffilter%` is used. the other files depend on
+  # relational associations with 'trip_id' that come from these 3 tables, so we
+  # use %chin%
 
   # 'trips' (trip_id)
 
@@ -61,7 +62,7 @@ filter_by_trip_id <- function(gtfs, trip_id, keep = TRUE) {
   gtfs <- filter_calendar_from_service_id(gtfs, relevant_services, `%chin%`)
   gtfs <- filter_calend_dates_from_service_id(gtfs, relevant_services, `%chin%`)
 
-  # 'routes' and 'fare_rules' (route_id)
+  # 'routes', 'fare_rules' and 'transfers' (route_id)
   #
   # we can use 'routes' to filter agency via routes -> agency_id, but we can
   # also use 'fare_rules' to filter it via fare_rules -> fare_id ->
@@ -69,6 +70,7 @@ filter_by_trip_id <- function(gtfs, trip_id, keep = TRUE) {
   # so we create a 'relevant_agencies' vector that holds the relevant
   # agency_ids from both paths and use all of them to filter agency later.
 
+  gtfs <- filter_transfers_from_route_id(gtfs, relevant_routes, `%chin%`)
   gtfs <- filter_routes_from_route_id(gtfs, relevant_routes, `%chin%`)
   gtfs <- filter_fare_rules_from_route_id(gtfs, relevant_routes, `%chin%`)
   relevant_agencies_from_routes <- unique(gtfs$routes$agency_id)
@@ -121,5 +123,9 @@ filter_by_trip_id <- function(gtfs, trip_id, keep = TRUE) {
 
   gtfs <- filter_frequencies_from_trip_id(gtfs, trip_id, `%ffilter%`)
 
+  # 'transfers' (trip_id)
+
+  gtfs <- filter_transfers_from_trip_id(gtfs, trip_id, `%ffilter%`)
+
   return(gtfs)
 }
diff --git a/R/filter_helpers.R b/R/filter_helpers.R
index e722163..d032243 100644
--- a/R/filter_helpers.R
+++ b/R/filter_helpers.R
@@ -168,9 +168,43 @@ filter_transfers_from_stop_id <- function(gtfs, relevant_stops, `%ffilter%`) {
       from_to_stop_id,
       rep("character", 2)
     )
+    gtfs$transfers <- gtfs$transfers[from_stop_id %ffilter% relevant_stops]
+    gtfs$transfers <- gtfs$transfers[to_stop_id %ffilter% relevant_stops]
+  }
+
+  return(gtfs)
+}
+
+filter_transfers_from_route_id <- function(gtfs, relevant_routes, `%ffilter%`) {
+  if (gtfsio::check_field_exists(gtfs, "transfers", "from_route_id")) {
+    gtfsio::assert_field_class(gtfs, "transfers", "from_route_id", "character")
+    gtfs$transfers <- gtfs$transfers[
+      from_route_id %chin% "" | from_route_id %ffilter% relevant_routes
+    ]
+  }
+
+  if (gtfsio::check_field_exists(gtfs, "transfers", "to_route_id")) {
+    gtfsio::assert_field_class(gtfs, "transfers", "to_route_id", "character")
+    gtfs$transfers <- gtfs$transfers[
+      to_route_id %chin% "" | to_route_id %ffilter% relevant_routes
+    ]
+  }
+
+  return(gtfs)
+}
+
+filter_transfers_from_trip_id <- function(gtfs, relevant_trips, `%ffilter%`) {
+  if (gtfsio::check_field_exists(gtfs, "transfers", "from_trip_id")) {
+    gtfsio::assert_field_class(gtfs, "transfers", "from_trip_id", "character")
+    gtfs$transfers <- gtfs$transfers[
+      from_trip_id %chin% "" | from_trip_id %ffilter% relevant_trips
+    ]
+  }
+
+  if (gtfsio::check_field_exists(gtfs, "transfers", "to_trip_id")) {
+    gtfsio::assert_field_class(gtfs, "transfers", "to_trip_id", "character")
     gtfs$transfers <- gtfs$transfers[
-      from_stop_id %ffilter% relevant_stops &
-        to_stop_id %ffilter% relevant_stops
+      to_trip_id %chin% "" | to_trip_id %ffilter% relevant_trips
     ]
   }
 
diff --git a/R/gtfstools.R b/R/gtfstools.R
index 7398235..99cea02 100644
--- a/R/gtfstools.R
+++ b/R/gtfstools.R
@@ -97,6 +97,10 @@ utils::globalVariables(
     "feed_start_date",
     "feed_end_date",
     "dist_to_prev_point",
-    "shape_dist_traveled"
+    "shape_dist_traveled",
+    "from_route_id",
+    "to_route_id",
+    "from_trip_id",
+    "to_trip_id"
   )
 )