diff --git a/esphome/components/http_request/__init__.py b/esphome/components/http_request/__init__.py
index 64d74323d6..80f03993ac 100644
--- a/esphome/components/http_request/__init__.py
+++ b/esphome/components/http_request/__init__.py
@@ -302,10 +302,14 @@ async def http_request_action_to_code(config, action_id, template_arg, args):
             lambda_ = await cg.process_lambda(json_, args_, return_type=cg.void)
             cg.add(var.set_json(lambda_))
         else:
+            cg.add(var.init_json(len(json_)))
             for key in json_:
                 template_ = await cg.templatable(json_[key], args, cg.std_string)
                 cg.add(var.add_json(key, template_))
-    for key, value in config.get(CONF_REQUEST_HEADERS, {}).items():
+    request_headers = config.get(CONF_REQUEST_HEADERS, {})
+    if request_headers:
+        cg.add(var.init_request_headers(len(request_headers)))
+    for key, value in request_headers.items():
         template_ = await cg.templatable(value, args, cg.const_char_ptr)
         cg.add(var.add_request_header(key, template_))
 
diff --git a/esphome/components/http_request/http_request.h b/esphome/components/http_request/http_request.h
index 17aeeba7d0..d16d3fe4a2 100644
--- a/esphome/components/http_request/http_request.h
+++ b/esphome/components/http_request/http_request.h
@@ -399,12 +399,14 @@ template<typename... Ts> class HttpRequestSendAction : public Action<Ts...> {
   TEMPLATABLE_VALUE(bool, capture_response)
 #endif
 
+  void init_request_headers(size_t count) { this->request_headers_.init(count); }
   void add_request_header(const char *key, TemplatableValue<const char *, Ts...> value) {
     this->request_headers_.push_back({key, value});
   }
 
   void add_collect_header(const char *value) { this->collect_headers_.push_back(value); }
 
+  void init_json(size_t count) { this->json_.init(count); }
   void add_json(const char *key, TemplatableValue<std::string, Ts...> value) { this->json_.push_back({key, value}); }
 
   void set_json(std::function<void(Ts..., JsonObject)> json_func) { this->json_func_ = json_func; }
@@ -507,9 +509,9 @@ template<typename... Ts> class HttpRequestSendAction : public Action<Ts...> {
   }
   void encode_json_func_(Ts... x, JsonObject root) { this->json_func_(x..., root); }
   HttpRequestComponent *parent_;
-  std::vector<std::pair<const char *, TemplatableValue<const char *, Ts...>>> request_headers_{};
+  FixedVector<std::pair<const char *, TemplatableValue<const char *, Ts...>>> request_headers_{};
   std::vector<std::string> collect_headers_{"content-type", "content-length"};
-  std::vector<std::pair<const char *, TemplatableValue<std::string, Ts...>>> json_{};
+  FixedVector<std::pair<const char *, TemplatableValue<std::string, Ts...>>> json_{};
   std::function<void(Ts..., JsonObject)> json_func_{nullptr};
 #ifdef USE_HTTP_REQUEST_RESPONSE
   Trigger<std::shared_ptr<HttpContainer>, std::string &, Ts...> success_trigger_with_response_;