diff --git a/esphome/components/online_image/__init__.py b/esphome/components/online_image/__init__.py
index d9a7609543..dfb10137aa 100644
--- a/esphome/components/online_image/__init__.py
+++ b/esphome/components/online_image/__init__.py
@@ -125,7 +125,7 @@ async def online_image_action_to_code(config, action_id, template_arg, args):
     var = cg.new_Pvariable(action_id, template_arg, paren)
 
     if CONF_URL in config:
-        template_ = await cg.templatable(config[CONF_URL], args, cg.const_char_ptr)
+        template_ = await cg.templatable(config[CONF_URL], args, cg.std_string)
         cg.add(var.set_url(template_))
     return var
 
diff --git a/esphome/components/online_image/online_image.h b/esphome/components/online_image/online_image.h
index 775cc46e0b..51c11478cd 100644
--- a/esphome/components/online_image/online_image.h
+++ b/esphome/components/online_image/online_image.h
@@ -157,7 +157,7 @@ class OnlineImage : public PollingComponent,
 template<typename... Ts> class OnlineImageSetUrlAction : public Action<Ts...> {
  public:
   OnlineImageSetUrlAction(OnlineImage *parent) : parent_(parent) {}
-  TEMPLATABLE_VALUE(const char *, url)
+  TEMPLATABLE_VALUE(std::string, url)
   void play(Ts... x) override {
     this->parent_->set_url(this->url_.value(x...));
     this->parent_->update();
@@ -170,7 +170,6 @@ template<typename... Ts> class OnlineImageSetUrlAction : public Action<Ts...> {
 template<typename... Ts> class OnlineImageReleaseAction : public Action<Ts...> {
  public:
   OnlineImageReleaseAction(OnlineImage *parent) : parent_(parent) {}
-  TEMPLATABLE_VALUE(const char *, url)
   void play(Ts... x) override { this->parent_->release(); }
 
  protected:
diff --git a/tests/components/online_image/common-esp32.yaml b/tests/components/online_image/common-esp32.yaml
index d3a304cdc0..787a1ad368 100644
--- a/tests/components/online_image/common-esp32.yaml
+++ b/tests/components/online_image/common-esp32.yaml
@@ -4,13 +4,13 @@ spi:
   - id: spi_main_lcd
     clk_pin: 16
     mosi_pin: 17
-    miso_pin: 15
+    miso_pin: 18
 
 display:
   - platform: ili9xxx
     id: main_lcd
     model: ili9342
-    cs_pin: 12
+    cs_pin: 20
     dc_pin: 13
     reset_pin: 21
     invert_colors: true
diff --git a/tests/components/online_image/common.yaml b/tests/components/online_image/common.yaml
index 8f7ea6238b..5c6feb4c81 100644
--- a/tests/components/online_image/common.yaml
+++ b/tests/components/online_image/common.yaml
@@ -34,4 +34,12 @@ time:
           - online_image.set_url:
               id: online_rgba_image
               url: http://www.example.org/example.png
+          - online_image.set_url:
+              id: online_rgba_image
+              url: !lambda |-
+                return "http://www.example.org/example.png";
+          - online_image.set_url:
+              id: online_rgba_image
+              url: !lambda |-
+                return str_sprintf("http://homeassistant.local:8123");