diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index 76e2dbdb71..4cfea4c9d6 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -239,6 +239,15 @@ endif::git-rev-list[]
    `false`, `off`, `no` to show the non-trailer lines. If option is
    given without value it is enabled. If given multiple times the last
    value is used.
+** 'separator=<SEP>': specify a separator inserted between trailer
+   lines. When this option is not given each trailer line is
+   terminated with a line feed character. The string SEP may contain
+   the literal formatting codes described above. To use comma as
+   separator one must use `%x2C` as it would otherwise be parsed as
+   next option. If separator option is given multiple times only the
+   last one is used. E.g., `%(trailers:key=Ticket,separator=%x2C )`
+   shows all trailer lines whose key is "Ticket" separated by a comma
+   and a space.
 ** 'unfold[=val]': make it behave as if interpret-trailer's `--unfold`
    option was given. In same way as to for `only` it can be followed
    by an equal sign and explicit value. E.g.,
diff --git a/pretty.c b/pretty.c
index 2c66698b89..6d58b21aff 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1361,6 +1361,7 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 	if (skip_prefix(placeholder, "(trailers", &arg)) {
 		struct process_trailer_options opts = PROCESS_TRAILER_OPTIONS_INIT;
 		struct string_list filter_list = STRING_LIST_INIT_NODUP;
+		struct strbuf sepbuf = STRBUF_INIT;
 		size_t ret = 0;
 
 		opts.no_divider = 1;
@@ -1384,6 +1385,14 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 					opts.filter = format_trailer_match_cb;
 					opts.filter_data = &filter_list;
 					opts.only_trailers = 1;
+				} else if (match_placeholder_arg_value(arg, "separator", &arg, &argval, &arglen)) {
+					char *fmt;
+
+					strbuf_reset(&sepbuf);
+					fmt = xstrndup(argval, arglen);
+					strbuf_expand(&sepbuf, fmt, strbuf_expand_literal_cb, NULL);
+					free(fmt);
+					opts.separator = &sepbuf;
 				} else if (!match_placeholder_bool_arg(arg, "only", &arg, &opts.only_trailers) &&
 					   !match_placeholder_bool_arg(arg, "unfold", &arg, &opts.unfold) &&
 					   !match_placeholder_bool_arg(arg, "valueonly", &arg, &opts.value_only))
@@ -1396,6 +1405,7 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 		}
 	trailer_out:
 		string_list_clear(&filter_list, 0);
+		strbuf_release(&sepbuf);
 		return ret;
 	}
 
diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh
index 1ad6834781..99f50fa401 100755
--- a/t/t4205-log-pretty-formats.sh
+++ b/t/t4205-log-pretty-formats.sh
@@ -679,6 +679,42 @@ test_expect_success '%(trailers:key=foo,valueonly) shows only value' '
 	test_cmp expect actual
 '
 
+test_expect_success 'pretty format %(trailers:separator) changes separator' '
+	git log --no-walk --pretty=format:"X%(trailers:separator=%x00,unfold)X" >actual &&
+	printf "XSigned-off-by: A U Thor <author@example.com>\0Acked-by: A U Thor <author@example.com>\0[ v2 updated patch description ]\0Signed-off-by: A U Thor <author@example.com>X" >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'pretty format %(trailers) combining separator/key/valueonly' '
+	git commit --allow-empty -F - <<-\EOF &&
+	Important fix
+
+	The fix is explained here
+
+	Closes: #1234
+	EOF
+
+	git commit --allow-empty -F - <<-\EOF &&
+	Another fix
+
+	The fix is explained here
+
+	Closes: #567
+	Closes: #890
+	EOF
+
+	git commit --allow-empty -F - <<-\EOF &&
+	Does not close any tickets
+	EOF
+
+	git log --pretty="%s% (trailers:separator=%x2c%x20,key=Closes,valueonly)" HEAD~3.. >actual &&
+	test_write_lines \
+		"Does not close any tickets" \
+		"Another fix #567, #890" \
+		"Important fix #1234" >expect &&
+	test_cmp expect actual
+'
+
 test_expect_success 'trailer parsing not fooled by --- line' '
 	git commit --allow-empty -F - <<-\EOF &&
 	this is the subject
diff --git a/trailer.c b/trailer.c
index d0d9e91631..0c414f2fed 100644
--- a/trailer.c
+++ b/trailer.c
@@ -1129,10 +1129,11 @@ static void format_trailer_info(struct strbuf *out,
 				const struct trailer_info *info,
 				const struct process_trailer_options *opts)
 {
+	size_t origlen = out->len;
 	size_t i;
 
 	/* If we want the whole block untouched, we can take the fast path. */
-	if (!opts->only_trailers && !opts->unfold && !opts->filter) {
+	if (!opts->only_trailers && !opts->unfold && !opts->filter && !opts->separator) {
 		strbuf_add(out, info->trailer_start,
 			   info->trailer_end - info->trailer_start);
 		return;
@@ -1150,16 +1151,26 @@ static void format_trailer_info(struct strbuf *out,
 			if (!opts->filter || opts->filter(&tok, opts->filter_data)) {
 				if (opts->unfold)
 					unfold_value(&val);
+
+				if (opts->separator && out->len != origlen)
+					strbuf_addbuf(out, opts->separator);
 				if (!opts->value_only)
 					strbuf_addf(out, "%s: ", tok.buf);
 				strbuf_addbuf(out, &val);
-				strbuf_addch(out, '\n');
+				if (!opts->separator)
+					strbuf_addch(out, '\n');
 			}
 			strbuf_release(&tok);
 			strbuf_release(&val);
 
 		} else if (!opts->only_trailers) {
+			if (opts->separator && out->len != origlen) {
+				strbuf_addbuf(out, opts->separator);
+			}
 			strbuf_addstr(out, trailer);
+			if (opts->separator) {
+				strbuf_rtrim(out);
+			}
 		}
 	}
 
diff --git a/trailer.h b/trailer.h
index 06d417fe93..203acf4ee1 100644
--- a/trailer.h
+++ b/trailer.h
@@ -73,6 +73,7 @@ struct process_trailer_options {
 	int unfold;
 	int no_divider;
 	int value_only;
+	const struct strbuf *separator;
 	int (*filter)(const struct strbuf *, void *);
 	void *filter_data;
 };