diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5f837b3d6..304b59a0f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
  - #1871, Fix OpenAPI missing default values for String types and identify Array types as "array" instead of "string" - @laurenceisla
  - #1930, Fix RPC return type handling for `RETURNS TABLE` with a single column. Regression of #1615. - @wolfgangwalther
+ - #1938, Fix using single double quotes(`"`) and backslashes(`/`) as values on the "in" operator - @steve-chavez
 
 ### Changed
 
diff --git a/src/PostgREST/Query/SqlFragment.hs b/src/PostgREST/Query/SqlFragment.hs
index 7ecb283ba..d1ec13550 100644
--- a/src/PostgREST/Query/SqlFragment.hs
+++ b/src/PostgREST/Query/SqlFragment.hs
@@ -123,7 +123,8 @@ normalizedBody body =
 singleParameter :: Maybe BL.ByteString -> ByteString -> H.Snippet
 singleParameter body typ =
   if typ == "bytea"
-    then H.encoderAndParam (HE.nullable HE.bytea) (toS <$> body) -- needed because bytea fails with HE.unknown(pg tries to utf8 encode)
+    -- TODO: Hasql fails when using HE.unknown with bytea(pg tries to utf8 encode).
+    then H.encoderAndParam (HE.nullable HE.bytea) (toS <$> body)
     else H.encoderAndParam (HE.nullable HE.unknown) (toS <$> body) <> "::" <> H.sql typ
 
 selectBody :: SqlFragment
@@ -138,6 +139,15 @@ pgFmtLit x =
    then "E" <> slashed
    else slashed
 
+-- Here we build the pg array literal, e.g '{"Hebdon, John","Other","Another"}', manually.
+-- This is necessary to pass an "unknown" array and let pg infer the type.
+pgFmtArrayLit :: [Text] -> Text
+pgFmtArrayLit vals =
+ let trimmed = trimNullChars
+     slashed = T.replace "\\" "\\\\" . trimmed
+     escaped x = "\"" <> T.replace "\"" "\\\"" (slashed x) <> "\"" in
+ "{" <> T.intercalate "," (escaped <$> vals) <> "}"
+
 -- TODO: refactor by following https://github.com/PostgREST/postgrest/pull/1631#issuecomment-711070833
 pgFmtIdent :: Text -> SqlFragment
 pgFmtIdent x = encodeUtf8 $ "\"" <> T.replace "\"" "\"\"" (trimNullChars x) <> "\""
@@ -220,12 +230,9 @@ pgFmtFilter table (Filter fld (OpExpr hasNot oper)) = notOp <> " " <> case oper
    -- We don't use "IN", we use "= ANY". IN has the following disadvantages:
    -- + No way to use an empty value on IN: "col IN ()" is invalid syntax. With ANY we can do "= ANY('{}')"
    -- + Can invalidate prepared statements: multiple parameters on an IN($1, $2, $3) will lead to using different prepared statements and not take advantage of caching.
-   In vals -> pgFmtField table fld <> " " <>
-    case vals of
+   In vals -> pgFmtField table fld <> " " <> case vals of
       [""] -> "= ANY('{}') "
-      -- Here we build the pg array, e.g '{"Hebdon, John","Other","Another"}', manually. We quote the values to prevent the "," being treated as an element separator.
-      -- TODO: Ideally this would be done on Hasql with an encoder, but the "array unknown" is not working(Hasql doesn't pass any value).
-      _    -> "= ANY (" <> unknownLiteral ("{" <> T.intercalate "," ((\x -> "\"" <> x <> "\"") <$> vals) <> "}") <> ")"
+      _    -> "= ANY (" <> unknownLiteral (pgFmtArrayLit vals) <> ") "
 
    Fts op lang val ->
      pgFmtFieldOp op <> "(" <> ftsLang lang <> unknownLiteral val <> ") "
diff --git a/test/Feature/QuerySpec.hs b/test/Feature/QuerySpec.hs
index 57f989d1d..350216dc4 100644
--- a/test/Feature/QuerySpec.hs
+++ b/test/Feature/QuerySpec.hs
@@ -938,25 +938,37 @@ spec actualPgVersion = do
       get "/w_or_wo_comma_names?name=in.(\"Hebdon, John\",\"Williams, Mary\",\"Smith, Joseph\")" `shouldRespondWith`
         [json| [{"name":"Hebdon, John"},{"name":"Williams, Mary"},{"name":"Smith, Joseph"}] |]
         { matchHeaders = [matchContentTypeJson] }
-      get "/w_or_wo_comma_names?name=not.in.(\"Hebdon, John\",\"Williams, Mary\",\"Smith, Joseph\")" `shouldRespondWith`
-        [json| [{"name":"David White"},{"name":"Larry Thompson"},{"name":"Double O Seven(007)"}] |]
+      get "/w_or_wo_comma_names?name=not.in.(\"Hebdon, John\",\"Williams, Mary\",\"Smith, Joseph\")&limit=3" `shouldRespondWith`
+        [json| [ { "name": "David White" }, { "name": "Larry Thompson" }, { "name": "Double O Seven(007)" }] |]
         { matchHeaders = [matchContentTypeJson] }
 
     it "succeeds w/ and w/o quoted values" $ do
       get "/w_or_wo_comma_names?name=in.(David White,\"Hebdon, John\")" `shouldRespondWith`
         [json| [{"name":"Hebdon, John"},{"name":"David White"}] |]
         { matchHeaders = [matchContentTypeJson] }
-      get "/w_or_wo_comma_names?name=not.in.(\"Hebdon, John\",Larry Thompson,\"Smith, Joseph\")" `shouldRespondWith`
-        [json| [{"name":"Williams, Mary"},{"name":"David White"},{"name":"Double O Seven(007)"}] |]
+      get "/w_or_wo_comma_names?name=not.in.(\"Hebdon, John\",Larry Thompson,\"Smith, Joseph\")&limit=3" `shouldRespondWith`
+        [json| [ { "name": "Williams, Mary" }, { "name": "David White" }, { "name": "Double O Seven(007)" }] |]
         { matchHeaders = [matchContentTypeJson] }
       get "/w_or_wo_comma_names?name=in.(\"Double O Seven(007)\")" `shouldRespondWith`
         [json| [{"name":"Double O Seven(007)"}] |]
         { matchHeaders = [matchContentTypeJson] }
 
-    it "fails on malformed quoted values" $ do
-      get "/w_or_wo_comma_names?name=in.(\"\"Hebdon, John\")" `shouldRespondWith` 400
-      get "/w_or_wo_comma_names?name=in.(\"\"Hebdon, John\"\"Mary)" `shouldRespondWith` 400
-      get "/w_or_wo_comma_names?name=in.(Williams\"Hebdon, John\")" `shouldRespondWith` 400
+  describe "IN values without quotes" $ do
+    it "accepts single double quotes as values" $ do
+      get "/w_or_wo_comma_names?name=in.(\")" `shouldRespondWith`
+        [json| [{ "name": "\"" }] |]
+        { matchHeaders = [matchContentTypeJson] }
+      get "/w_or_wo_comma_names?name=in.(Double\"Quote\"McGraw\")" `shouldRespondWith`
+        [json| [ { "name": "Double\"Quote\"McGraw\"" } ] |]
+        { matchHeaders = [matchContentTypeJson] }
+
+    it "accepts backslashes as values" $ do
+      get "/w_or_wo_comma_names?name=in.(\\)" `shouldRespondWith`
+        [json| [{ "name": "\\" }] |]
+        { matchHeaders = [matchContentTypeJson] }
+      get "/w_or_wo_comma_names?name=in.(/\\Slash/\\Beast/\\)" `shouldRespondWith`
+        [json| [ { "name": "/\\Slash/\\Beast/\\" } ] |]
+        { matchHeaders = [matchContentTypeJson] }
 
   describe "IN and NOT IN empty set" $ do
     context "returns an empty result for IN when no value is present" $ do
diff --git a/test/fixtures/data.sql b/test/fixtures/data.sql
index 8fb81404a..5104c1777 100644
--- a/test/fixtures/data.sql
+++ b/test/fixtures/data.sql
@@ -345,6 +345,10 @@ INSERT INTO w_or_wo_comma_names VALUES ('Smith, Joseph');
 INSERT INTO w_or_wo_comma_names VALUES ('David White');
 INSERT INTO w_or_wo_comma_names VALUES ('Larry Thompson');
 INSERT INTO w_or_wo_comma_names VALUES ('Double O Seven(007)');
+INSERT INTO w_or_wo_comma_names VALUES ('"');
+INSERT INTO w_or_wo_comma_names VALUES ('Double"Quote"McGraw"');
+INSERT INTO w_or_wo_comma_names VALUES ('\');
+INSERT INTO w_or_wo_comma_names VALUES ('/\Slash/\Beast/\');
 
 TRUNCATE TABLE items_with_different_col_types CASCADE;
 INSERT INTO items_with_different_col_types VALUES (1, null, null, null, null, null, null, null);