diff --git a/changelog/unreleased/kong/grpc-web-large-req-error.yml b/changelog/unreleased/kong/grpc-web-large-req-error.yml
new file mode 100644
index 00000000000..b91b5d429ad
--- /dev/null
+++ b/changelog/unreleased/kong/grpc-web-large-req-error.yml
@@ -0,0 +1,3 @@
+message: "**grpc-web**: fix an issue where large requests would result in an error"
+type: bugfix
+scope: Plugin
diff --git a/kong/plugins/grpc-web/handler.lua b/kong/plugins/grpc-web/handler.lua
index 8159fb5c196..767aa9c478a 100644
--- a/kong/plugins/grpc-web/handler.lua
+++ b/kong/plugins/grpc-web/handler.lua
@@ -7,6 +7,7 @@ local ngx = ngx
 local kong = kong
 
 local string_format = string.format
+local io_open = io.open
 
 local ngx_arg = ngx.arg
 local ngx_var = ngx.var
@@ -15,10 +16,12 @@ local kong_request_get_path = kong.request.get_path
 local kong_request_get_header = kong.request.get_header
 local kong_request_get_method = kong.request.get_method
 local kong_request_get_raw_body = kong.request.get_raw_body
+local ngx_req_get_body_file = ngx.req.get_body_file
 local kong_response_exit = kong.response.exit
 local kong_response_set_header = kong.response.set_header
 local kong_service_request_set_header = kong.service.request.set_header
 local kong_service_request_set_raw_body = kong.service.request.set_raw_body
+local warn = kong.log.warn
 
 
 local grpc_web = {
@@ -34,6 +37,26 @@ local CORS_HEADERS = {
   ["Access-Control-Allow-Headers"] = "content-type,x-grpc-web,x-user-agent",
 }
 
+local function get_body()
+  local body, err = kong_request_get_raw_body()
+  if body then
+    return body
+  end
+
+  -- if body_file is not nil, the error of get_raw_body is expected
+  -- otherwise return the error
+  local body_file = ngx_req_get_body_file()
+  assert(body_file, err)
+
+  warn("client_body_buffer_size exceeded and reading the request from disk. Please consider increasing the value.")
+
+  local file = assert(io_open(body_file, "rb"))
+  body = assert(file:read("*a"))
+  file:close()
+
+  return body
+end
+
 function grpc_web:access(conf)
   kong_response_set_header("Access-Control-Allow-Origin", conf.allow_origin_header)
 
@@ -63,7 +86,7 @@ function grpc_web:access(conf)
 
   kong_service_request_set_header("Content-Type", "application/grpc")
   kong_service_request_set_header("TE", "trailers")
-  kong_service_request_set_raw_body(dec:upstream(kong_request_get_raw_body()))
+  kong_service_request_set_raw_body(dec:upstream(get_body()))
 end
 
 
diff --git a/spec/03-plugins/32-grpc-web/01-proxy_spec.lua b/spec/03-plugins/32-grpc-web/01-proxy_spec.lua
index 8c37776204a..de03b456f55 100644
--- a/spec/03-plugins/32-grpc-web/01-proxy_spec.lua
+++ b/spec/03-plugins/32-grpc-web/01-proxy_spec.lua
@@ -22,6 +22,10 @@ for _, strategy in helpers.each_strategy() do
         "gAAAAB5ncnBjLXN0YXR1czowDQpncnBjLW1lc3NhZ2U6DQo="
     local HELLO_RESPONSE_BODY = ngx.decode_base64("AAAAAAwKCmhlbGxvIGhleWE=") ..
         ngx.decode_base64("gAAAAB5ncnBjLXN0YXR1czowDQpncnBjLW1lc3NhZ2U6DQo=")
+    -- larger than 1k
+    local LARGE_MESSAGE = string.rep("OK", 10000)
+    local LARGE_REQUEST_BODY = '{"greeting": \"' .. LARGE_MESSAGE .. '\"}'
+    local LARGE_RESPONSE_BODY = '{"reply":\"hello ' .. LARGE_MESSAGE .. '\"}'
 
     lazy_setup(function()
       local bp = helpers.get_db_utils(strategy, {
@@ -78,7 +82,7 @@ for _, strategy in helpers.each_strategy() do
     end)
 
     lazy_teardown(function()
-      helpers.stop_kong()
+      helpers.stop_kong(nil, true)
     end)
 
 
@@ -155,7 +159,7 @@ for _, strategy in helpers.each_strategy() do
       assert.is_nil(err)
     end)
 
-     test("Call plain JSON via HTTP", function()
+    test("Call plain JSON via HTTP", function()
       local res, err = proxy_client:post("/hello.HelloService/SayHello", {
         headers = {
           ["Content-Type"] = "application/json",
@@ -167,16 +171,31 @@ for _, strategy in helpers.each_strategy() do
       assert.is_nil(err)
     end)
 
-     test("Pass stripped URI", function()
-       local res, err = proxy_client:post("/prefix/hello.HelloService/SayHello", {
-         headers = {
-           ["Content-Type"] = "application/json",
-         },
-         body = cjson.encode{ greeting = "heya" },
-       })
-
-       assert.same({ reply = "hello heya" }, cjson.decode((res:read_body())))
-       assert.is_nil(err)
-     end)
+    test("Pass stripped URI", function()
+      local res, err = proxy_client:post("/prefix/hello.HelloService/SayHello", {
+        headers = {
+          ["Content-Type"] = "application/json",
+        },
+        body = cjson.encode{ greeting = "heya" },
+      })
+
+      assert.same({ reply = "hello heya" }, cjson.decode((res:read_body())))
+      assert.is_nil(err)
+    end)
+
+    test("#regression large body causes error", function()
+      local res = assert(proxy_client:post("/hello.HelloService/SayHello", {
+        headers = {
+          ["Content-Type"] = "application/json",
+          ["Content-Length"] = tostring(#LARGE_REQUEST_BODY),
+        },
+        body = LARGE_REQUEST_BODY,
+      }))
+
+      local body = assert(res:read_body())
+      assert.equal(LARGE_RESPONSE_BODY, body)
+
+      assert.logfile().has.line("client_body_buffer_size exceeded")
+    end)
  end)
 end