diff --git a/changes.d/6480.fix.md b/changes.d/6480.fix.md
new file mode 100644
index 00000000000..0e37017a995
--- /dev/null
+++ b/changes.d/6480.fix.md
@@ -0,0 +1 @@
+`cat-log`: List log files which are available via a configured tailer/viewer command.
diff --git a/cylc/flow/scripts/cat_log.py b/cylc/flow/scripts/cat_log.py
index ec652287044..2b4f03ca696 100755
--- a/cylc/flow/scripts/cat_log.py
+++ b/cylc/flow/scripts/cat_log.py
@@ -596,28 +596,51 @@ def _main(
                 cmd.append('--prepend-path')
             cmd.append(workflow_id)
             # TODO: Add Intelligent Host selection to this
+            proc = None
             with suppress(KeyboardInterrupt):
                 # (Ctrl-C while tailing)
                 # NOTE: This will raise NoHostsError if the platform is not
                 # contactable
-                remote_cylc_cmd(
+                proc = remote_cylc_cmd(
                     cmd,
                     platform,
-                    capture_process=False,
+                    capture_process=(mode == 'list-dir'),
                     manage=(mode == 'tail'),
-                    text=False
+                    text=(mode == 'list-dir'),
                 )
-            if (
-                mode == 'list-dir'
-                and os.path.exists(
-                    os.path.join(
-                        local_log_dir,
-                        'job-activity.log'
-                    )
-                )
-            ):
-                # add the local-only job-activity.log file to the remote-list
-                print('job-activity.log')
+
+            # add and missing items to file listing results
+            if isinstance(proc, Popen):
+                # i.e: if mode=='list-dir' and ctrl+c not pressed
+                out, err = proc.communicate()
+                files = out.splitlines()
+
+                # add files which can be accessed via a tailer
+                if live_job_id is not None:
+                    if (
+                        # NOTE: only list the file if it can be viewed in
+                        # both modes
+                        (platform['out tailer'] and platform['out viewer'])
+                        and 'job.out' not in files
+                    ):
+                        files.append('job.out')
+                    if (
+                        (platform['err tailer'] and platform['err viewer'])
+                        and 'job.err' not in files
+                    ):
+                        files.append('job.err')
+
+                # add the job-activity.log file which is always local
+                if os.path.exists(
+                    os.path.join(local_log_dir, 'job-activity.log')
+                ):
+                    files.append('job-activity.log')
+
+                files.sort()
+                print('\n'.join(files))
+                print(err, file=sys.stderr)
+                sys.exit(proc.returncode)
+
         else:
             # Local task job or local job log.
             logpath = os.path.join(local_log_dir, options.filename)
diff --git a/tests/functional/cylc-cat-log/13-remote-out-err-tailer.t b/tests/functional/cylc-cat-log/13-remote-out-err-tailer.t
new file mode 100644
index 00000000000..c1c562495ce
--- /dev/null
+++ b/tests/functional/cylc-cat-log/13-remote-out-err-tailer.t
@@ -0,0 +1,87 @@
+#!/usr/bin/env bash
+# THIS FILE IS PART OF THE CYLC WORKFLOW ENGINE.
+# Copyright (C) NIWA & British Crown (Met Office) & Contributors.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#-------------------------------------------------------------------------------
+# Test "cylc cat-log" with custom out/err tailers
+export REQUIRE_PLATFORM='loc:remote runner:background fs:indep comms:tcp'
+. "$(dirname "$0")/test_header"
+#-------------------------------------------------------------------------------
+set_test_number 12
+#-------------------------------------------------------------------------------
+# run the workflow
+TEST_NAME="${TEST_NAME_BASE}-validate"
+install_workflow "${TEST_NAME_BASE}" "${TEST_NAME_BASE}"
+run_ok "${TEST_NAME}" cylc validate "${WORKFLOW_NAME}"
+workflow_run_ok "${TEST_NAME_BASE}-run" cylc play -N "${WORKFLOW_NAME}"
+#-------------------------------------------------------------------------------
+# change the platform the task ran on to the remote platform
+sqlite3 "${HOME}/cylc-run/${WORKFLOW_NAME}/log/db" "
+  UPDATE
+    task_jobs
+  SET
+    platform_name = '${CYLC_TEST_PLATFORM}',
+    run_status = null
+  WHERE
+    name = 'foo'
+    AND cycle = '1'
+;"
+#-------------------------------------------------------------------------------
+# test cylc cat-log --mode=list-dir will not list job.out / err
+# (no tailer / viewer configured)
+create_test_global_config "" "
+[platforms]
+   [[$CYLC_TEST_PLATFORM]]
+      out tailer =
+      err tailer =
+      out viewer =
+      err viewer =
+  "
+TEST_NAME="${TEST_NAME_BASE}-list-dir-no-tailers"
+# NOTE: command will fail due to missing remote directory (this tests remote
+# error code is preserved)
+run_fail "${TEST_NAME}" cylc cat-log "${WORKFLOW_NAME}//1/foo" -m 'list-dir'
+# the job.out and job.err filees
+grep_fail "job.out" "${TEST_NAME}.stdout"
+grep_fail "job.err" "${TEST_NAME}.stdout"
+#-------------------------------------------------------------------------------
+# test cylc cat-log --mode=list-dir lists the tailed files
+# (both tailer and viewer configured)
+create_test_global_config "" "
+[platforms]
+   [[$CYLC_TEST_PLATFORM]]
+      out tailer = echo OUT
+      err tailer = echo ERR
+      out viewer = echo OUT
+      err viewer = echo ERR
+  "
+# test cylc cat-log --mode=list-dir lists the tailed files
+TEST_NAME="${TEST_NAME_BASE}-list-dir-with-tailers"
+# NOTE: command will fail due to missing remote directory (this tests remote
+# error code is preserved)
+run_fail "${TEST_NAME}" cylc cat-log "${WORKFLOW_NAME}//1/foo" -m 'list-dir'
+# the job.out and job.err filees
+grep_ok "job.out" "${TEST_NAME}.stdout"
+grep_ok "job.err" "${TEST_NAME}.stdout"
+#-------------------------------------------------------------------------------
+# test cylc cat-log runs the custom tailers
+TEST_NAME="${TEST_NAME_BASE}-cat-out"
+run_ok "${TEST_NAME}" cylc cat-log "${WORKFLOW_NAME}//1/foo" -f o -m t
+grep_ok "OUT" "${TEST_NAME}.stdout"
+run_ok "${TEST_NAME}" cylc cat-log "${WORKFLOW_NAME}//1/foo" -f e -m t
+grep_ok "ERR" "${TEST_NAME}.stdout"
+#-------------------------------------------------------------------------------
+purge
+exit
diff --git a/tests/functional/cylc-cat-log/13-remote-out-err-tailer/flow.cylc b/tests/functional/cylc-cat-log/13-remote-out-err-tailer/flow.cylc
new file mode 100644
index 00000000000..21113656994
--- /dev/null
+++ b/tests/functional/cylc-cat-log/13-remote-out-err-tailer/flow.cylc
@@ -0,0 +1,25 @@
+[scheduler]
+   [[events]]
+       abort on stall timeout = True
+       stall timeout = PT2M
+
+[scheduling]
+    [[graph]]
+        R1 = foo
+
+[runtime]
+    [[foo]]
+        script = """
+            # wait for the started message to be received
+            cylc__job__poll_grep_workflow_log -E 'foo.*running'
+
+            # remove the out/err files
+            rm "${CYLC_TASK_LOG_DIR}/job.out"
+            rm "${CYLC_TASK_LOG_DIR}/job.err"
+
+            # stop the workflow, orphaning this job
+            cylc stop --now --now "${CYLC_WORKFLOW_ID}" 2>/dev/null >/dev/null
+
+            # suppress any subsequent messages
+            rm "${CYLC_WORKFLOW_RUN_DIR}/.service/contact"
+        """