diff --git a/NAMESPACE b/NAMESPACE
index e2f4ff2a..112fc391 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -60,6 +60,7 @@ export(req_body_multipart)
 export(req_body_raw)
 export(req_cache)
 export(req_cookie_preserve)
+export(req_cookies_set)
 export(req_dry_run)
 export(req_error)
 export(req_headers)
diff --git a/NEWS.md b/NEWS.md
index 076e94d4..1f14699b 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,6 @@
 # httr2 (development version)
 
+* New `req_cookie_set()` allows you to set client side cookies (#369).
 * `req_body_file()` no longer leaks a connection if the response doesn't complete succesfully (#534).
 * `req_perform()` no longer displays a progress bar when sleeping during tests. You can override this behaviour by setting the option `httr2_progress`.
 * `req_cache()` now re-caches the response if the body is hasn't been modified but the headers have changed (#442).
diff --git a/R/req-cookies.R b/R/req-cookies.R
index 29291f4b..65e13159 100644
--- a/R/req-cookies.R
+++ b/R/req-cookies.R
@@ -1,37 +1,68 @@
-#' Preserve cookies across requests
+#' Set and preserve cookies
+#'
+#' @description
+#' Use `req_cookie_set()` to set client side cookies that are sent to the
+#' server.
 #'
 #' By default, httr2 uses a clean slate for every request meaning that cookies
-#' are not automatically preserved across requests. To preserve cookies, you
-#' must set a cookie file which will be read before and updated after each
-#' request.
+#' are not automatically preserved across requests. To preserve cookies, use
+#' `req_cookie_preserve()` along with the path to cookie file that will be
+#' read before and updated after each request.
 #'
 #' @inheritParams req_perform
 #' @param path A path to a file where cookies will be read from before and updated after the request.
 #' @export
 #' @examples
+#' # Use `req_cookies_set()` to set client-side cookies
+#' request(example_url()) |>
+#'   req_cookies_set(a = 1, b = 1) |>
+#'   req_dry_run()
+#'
+#' # Use `req_cookie_preserve()` to preserve server-side cookies across requests
 #' path <- tempfile()
-#' httpbin <- request(example_url()) |>
-#'   req_cookie_preserve(path)
 #'
-#' # Manually set two cookies
-#' httpbin |>
+#' # Set a server-side cookie
+#' request(example_url()) |>
+#'   req_cookie_preserve(path) |>
 #'   req_template("/cookies/set/:name/:value", name = "chocolate", value = "chip") |>
 #'   req_perform() |>
 #'   resp_body_json()
 #'
-#' httpbin |>
+#' # Set another sever-side cookie
+#' request(example_url()) |>
+#'   req_cookie_preserve(path) |>
 #'   req_template("/cookies/set/:name/:value", name = "oatmeal", value = "raisin") |>
 #'   req_perform() |>
 #'   resp_body_json()
 #'
+#' # Add a client side cookie
+#' request(example_url()) |>
+#'   req_url_path("/cookies/set") |>
+#'   req_cookie_preserve(path) |>
+#'   req_cookies_set(snicker = "doodle") |>
+#'   req_perform() |>
+#'   resp_body_json()
+#'
 #' # The cookie path has a straightforward format
 #' cat(readChar(path, nchars = 1e4))
 req_cookie_preserve <- function(req, path) {
   check_request(req)
   check_string(path, allow_empty = FALSE)
 
-  req_options(req,
-    cookiejar = path,
-    cookiefile = path
-  )
+  req_options(req, cookiejar = path, cookiefile = path)
+}
+
+#' @export
+#' @rdname req_cookie_preserve
+#' @param ... <[`dynamic-dots`][rlang::dyn-dots]>
+#'   Name-value pairs that define query parameters. Each value must be
+#'   an atomic vector, which is automatically escaped. To opt-out of escaping,
+#'   wrap strings in `I()`.
+req_cookies_set <- function(req, ...) {
+  check_request(req)
+  req_options(req, cookie = cookies_build(list2(...)))
+}
+
+cookies_build <- function(x, error_call = caller_env()) {
+  elements_build(x, "Cookies", ";", error_call = error_call)
 }
diff --git a/R/url.R b/R/url.R
index b4f3cf0c..8ffab225 100644
--- a/R/url.R
+++ b/R/url.R
@@ -165,8 +165,12 @@ query_parse <- function(x) {
 }
 
 query_build <- function(x, error_call = caller_env()) {
+  elements_build(x, "Query", "&", error_call = error_call)
+}
+
+elements_build <- function(x, name, collapse, error_call = caller_env()) {
   if (!is_list(x) || (!is_named(x) && length(x) > 0)) {
-    cli::cli_abort("Query must be a named list.", call = error_call)
+    cli::cli_abort("{name} must be a named list.", call = error_call)
   }
 
   x <- compact(x)
@@ -177,7 +181,7 @@ query_build <- function(x, error_call = caller_env()) {
   values <- map2_chr(x, names(x), format_query_param, error_call = error_call)
   names <- curl::curl_escape(names(x))
 
-  paste0(names, "=", values, collapse = "&")
+  paste0(names, "=", values, collapse = collapse)
 }
 
 format_query_param <- function(x,
diff --git a/man/req_cookie_preserve.Rd b/man/req_cookie_preserve.Rd
index 5bbcb23b..0ef9f237 100644
--- a/man/req_cookie_preserve.Rd
+++ b/man/req_cookie_preserve.Rd
@@ -2,37 +2,63 @@
 % Please edit documentation in R/req-cookies.R
 \name{req_cookie_preserve}
 \alias{req_cookie_preserve}
-\title{Preserve cookies across requests}
+\alias{req_cookies_set}
+\title{Set and preserve cookies}
 \usage{
 req_cookie_preserve(req, path)
+
+req_cookies_set(req, ...)
 }
 \arguments{
 \item{req}{A httr2 \link{request} object.}
 
 \item{path}{A path to a file where cookies will be read from before and updated after the request.}
+
+\item{...}{<\code{\link[rlang:dyn-dots]{dynamic-dots}}>
+Name-value pairs that define query parameters. Each value must be
+an atomic vector, which is automatically escaped. To opt-out of escaping,
+wrap strings in \code{I()}.}
 }
 \description{
+Use \code{req_cookie_set()} to set client side cookies that are sent to the
+server.
+
 By default, httr2 uses a clean slate for every request meaning that cookies
-are not automatically preserved across requests. To preserve cookies, you
-must set a cookie file which will be read before and updated after each
-request.
+are not automatically preserved across requests. To preserve cookies, use
+\code{req_cookie_preserve()} along with the path to cookie file that will be
+read before and updated after each request.
 }
 \examples{
+# Use `req_cookies_set()` to set client-side cookies
+request(example_url()) |>
+  req_cookies_set(a = 1, b = 1) |>
+  req_dry_run()
+
+# Use `req_cookie_preserve()` to preserve server-side cookies across requests
 path <- tempfile()
-httpbin <- request(example_url()) |>
-  req_cookie_preserve(path)
 
-# Manually set two cookies
-httpbin |>
+# Set a server-side cookie
+request(example_url()) |>
+  req_cookie_preserve(path) |>
   req_template("/cookies/set/:name/:value", name = "chocolate", value = "chip") |>
   req_perform() |>
   resp_body_json()
 
-httpbin |>
+# Set another sever-side cookie
+request(example_url()) |>
+  req_cookie_preserve(path) |>
   req_template("/cookies/set/:name/:value", name = "oatmeal", value = "raisin") |>
   req_perform() |>
   resp_body_json()
 
+# Add a client side cookie
+request(example_url()) |>
+  req_url_path("/cookies/set") |>
+  req_cookie_preserve(path) |>
+  req_cookies_set(snicker = "doodle") |>
+  req_perform() |>
+  resp_body_json()
+
 # The cookie path has a straightforward format
 cat(readChar(path, nchars = 1e4))
 }
diff --git a/tests/testthat/test-req-cookies.R b/tests/testthat/test-req-cookies.R
index 039362af..85d3cda4 100644
--- a/tests/testthat/test-req-cookies.R
+++ b/tests/testthat/test-req-cookies.R
@@ -20,3 +20,21 @@ test_that("can read/write cookies", {
   expect_mapequal(cookies, list(x = "a", y = "b", z = "c"))
 
 })
+
+test_that("can set cookies", {
+  resp <- request(example_url()) %>%
+    req_cookies_set(a = 1, b = 1) %>%
+    req_url_path("/cookies") %>%
+    req_perform()
+
+  expect_equal(resp_body_json(resp), list(cookies = list(a = "1", b = "1")))
+})
+
+test_that("cookie values are usually escaped", {
+  resp <- request(example_url()) %>%
+    req_cookies_set(a = I("%20"), b = "%") %>%
+    req_url_path("/cookies") %>%
+    req_perform()
+
+  expect_equal(resp_body_json(resp), list(cookies = list(a = "%20", b = "%25")))
+})