diff --git a/scrapy/commands/runspider.py b/scrapy/commands/runspider.py
index a98033dd1..59caa08b3 100644
--- a/scrapy/commands/runspider.py
+++ b/scrapy/commands/runspider.py
@@ -1,5 +1,6 @@
 import sys
 import os
+import warnings
 from importlib import import_module
 
 from scrapy.utils.spider import iter_spider_classes
@@ -83,7 +84,16 @@ class Command(ScrapyCommand):
         spclasses = list(iter_spider_classes(module))
         if not spclasses:
             raise UsageError("No spider found in file: %s\n" % filename)
+
+        self._check_multiple_spiders(spclasses)
+
         spidercls = spclasses.pop()
 
         self.crawler_process.crawl(spidercls, **opts.spargs)
         self.crawler_process.start()
+
+    def _check_multiple_spiders(self, spclasses):
+        if len(spclasses) > 1:
+            msg = ("\n\nThere are multiple spiders in this file: "
+                   "Only the last-defined spider '{}' will be run.\n".format(spclasses[-1].name))
+            warnings.warn(msg, UserWarning)
diff --git a/tests/test_commands.py b/tests/test_commands.py
index 922098668..f6dcdc03f 100644
--- a/tests/test_commands.py
+++ b/tests/test_commands.py
@@ -2,6 +2,7 @@ import os
 import sys
 import subprocess
 import tempfile
+import warnings
 from time import sleep
 from os.path import exists, join, abspath
 from shutil import rmtree, copytree
@@ -193,6 +194,24 @@ class MySpider(scrapy.Spider):
         return []
 """
 
+    debug_log_multiple_spiders = """
+import scrapy
+
+class FirstSpider(scrapy.Spider):
+    name = 'spider1'
+
+    def start_requests(self):
+        self.logger.debug("spider1 Works!")
+        return []
+
+class SecondSpider(scrapy.Spider):
+    name = 'spider2'
+
+    def start_requests(self):
+        self.logger.debug("spider2 Works!")
+        return []
+"""
+
     @contextmanager
     def _create_file(self, content, name):
         tmpdir = self.mktemp()
@@ -267,6 +286,15 @@ class BadSpider(scrapy.Spider):
         self.assertIn("start_requests", log)
         self.assertIn("badspider.py", log)
 
+    def test_runspider_multiple_spiders(self):
+        log = self.get_log(self.debug_log_multiple_spiders)
+        self.assertIn("multiple spiders in this file", log)
+        self.assertIn("DEBUG: spider2 Works!", log)
+        self.assertIn("INFO: Spider opened", log)
+        self.assertIn("INFO: Closing spider (finished)", log)
+        self.assertIn("INFO: Spider closed (finished)", log)
+
+
 
 class BenchCommandTest(CommandTest):