diff --git a/diff.h b/diff.h
index 0c51724493..436b574a23 100644
--- a/diff.h
+++ b/diff.h
@@ -80,6 +80,7 @@ typedef struct strbuf *(*diff_prefix_fn_t)(struct diff_options *opt, void *data)
 #define DIFF_OPT_OVERRIDE_SUBMODULE_CONFIG (1 << 27)
 #define DIFF_OPT_DIRSTAT_BY_LINE     (1 << 28)
 #define DIFF_OPT_FUNCCONTEXT         (1 << 29)
+#define DIFF_OPT_PICKAXE_IGNORE_CASE (1 << 30)
 
 #define DIFF_OPT_TST(opts, flag)    ((opts)->flags & DIFF_OPT_##flag)
 #define DIFF_OPT_SET(opts, flag)    ((opts)->flags |= DIFF_OPT_##flag)
diff --git a/diffcore-pickaxe.c b/diffcore-pickaxe.c
index 380a837b5b..ed23eb4bdd 100644
--- a/diffcore-pickaxe.c
+++ b/diffcore-pickaxe.c
@@ -138,8 +138,12 @@ static void diffcore_pickaxe_grep(struct diff_options *o)
 {
 	int err;
 	regex_t regex;
+	int cflags = REG_EXTENDED | REG_NEWLINE;
 
-	err = regcomp(&regex, o->pickaxe, REG_EXTENDED | REG_NEWLINE);
+	if (DIFF_OPT_TST(o, PICKAXE_IGNORE_CASE))
+		cflags |= REG_ICASE;
+
+	err = regcomp(&regex, o->pickaxe, cflags);
 	if (err) {
 		char errbuf[1024];
 		regerror(err, &regex, errbuf, 1024);
@@ -237,7 +241,8 @@ static void diffcore_pickaxe_count(struct diff_options *o)
 		}
 		regexp = &regex;
 	} else {
-		kws = kwsalloc(NULL);
+		kws = kwsalloc(DIFF_OPT_TST(o, PICKAXE_IGNORE_CASE)
+			       ? tolower_trans_tbl : NULL);
 		kwsincr(kws, needle, len);
 		kwsprep(kws);
 	}
diff --git a/revision.c b/revision.c
index 8764dde381..971b7dc98d 100644
--- a/revision.c
+++ b/revision.c
@@ -1559,6 +1559,7 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->grep_filter.regflags |= REG_EXTENDED;
 	} else if (!strcmp(arg, "--regexp-ignore-case") || !strcmp(arg, "-i")) {
 		revs->grep_filter.regflags |= REG_ICASE;
+		DIFF_OPT_SET(&revs->diffopt, PICKAXE_IGNORE_CASE);
 	} else if (!strcmp(arg, "--fixed-strings") || !strcmp(arg, "-F")) {
 		revs->grep_filter.fixed = 1;
 	} else if (!strcmp(arg, "--all-match")) {
diff --git a/t/t4209-log-pickaxe.sh b/t/t4209-log-pickaxe.sh
new file mode 100755
index 0000000000..eed727341d
--- /dev/null
+++ b/t/t4209-log-pickaxe.sh
@@ -0,0 +1,119 @@
+#!/bin/sh
+
+test_description='log --grep/--author/--regexp-ignore-case/-S/-G'
+. ./test-lib.sh
+
+test_expect_success setup '
+	>file &&
+	git add file &&
+	test_tick &&
+	git commit -m initial &&
+
+	echo Picked >file &&
+	test_tick &&
+	git commit -a --author="Another Person <another@example.com>" -m second
+'
+
+test_expect_success 'log --grep' '
+	git log --grep=initial --format=%H >actual &&
+	git rev-parse --verify HEAD^ >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log --grep --regexp-ignore-case' '
+	git log --regexp-ignore-case --grep=InItial --format=%H >actual &&
+	git rev-parse --verify HEAD^ >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log --grep -i' '
+	git log -i --grep=InItial --format=%H >actual &&
+	git rev-parse --verify HEAD^ >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log --author --regexp-ignore-case' '
+	git log --regexp-ignore-case --author=person --format=%H >actual &&
+	git rev-parse --verify HEAD >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log --author -i' '
+	git log -i --author=person --format=%H >actual &&
+	git rev-parse --verify HEAD >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log -G (nomatch)' '
+	git log -Gpicked --format=%H >actual &&
+	>expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log -G (match)' '
+	git log -GPicked --format=%H >actual &&
+	git rev-parse --verify HEAD >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log -G --regexp-ignore-case (nomatch)' '
+	git log --regexp-ignore-case -Gpickle --format=%H >actual &&
+	>expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log -G -i (nomatch)' '
+	git log -i -Gpickle --format=%H >actual &&
+	>expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log -G --regexp-ignore-case (match)' '
+	git log --regexp-ignore-case -Gpicked --format=%H >actual &&
+	git rev-parse --verify HEAD >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log -G -i (match)' '
+	git log -i -Gpicked --format=%H >actual &&
+	git rev-parse --verify HEAD >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log -S (nomatch)' '
+	git log -Spicked --format=%H >actual &&
+	>expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log -S (match)' '
+	git log -SPicked --format=%H >actual &&
+	git rev-parse --verify HEAD >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log -S --regexp-ignore-case (match)' '
+	git log --regexp-ignore-case -Spicked --format=%H >actual &&
+	git rev-parse --verify HEAD >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log -S -i (match)' '
+	git log -i -Spicked --format=%H >actual &&
+	git rev-parse --verify HEAD >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log -S --regexp-ignore-case (nomatch)' '
+	git log --regexp-ignore-case -Spickle --format=%H >actual &&
+	>expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log -S -i (nomatch)' '
+	git log -i -Spickle --format=%H >actual &&
+	>expect &&
+	test_cmp expect actual
+'
+
+test_done