diff --git a/AUTHORS b/AUTHORS
index eb3c016a570..fe96e0d79b3 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -59,6 +59,7 @@ Denis Kirisov
 Diego Russo
 Dmitry Dygalo
 Dmitry Pribysh
+Drew Ackerman
 Duncan Betts
 Edison Gustavo Muenz
 Edoardo Batini
diff --git a/_pytest/python_api.py b/_pytest/python_api.py
index 8e09a4a6fd3..bfd5f137274 100644
--- a/_pytest/python_api.py
+++ b/_pytest/python_api.py
@@ -443,12 +443,16 @@ def approx(expected, rel=None, abs=None, nan_ok=False):
     # This has the advantage that it made it easy to support mapping types
     # (i.e. dict).  The old code accepted mapping types, but would only compare
     # their keys, which is probably not what most people would expect.
-
-    if _is_numpy_array(expected):
+    if isinstance(expected, String):
+        raise TypeError("Strings can not be approximated")
+    elif _is_numpy_array(expected):
         cls = ApproxNumpy
     elif isinstance(expected, Mapping):
         cls = ApproxMapping
     elif isinstance(expected, Sequence) and not isinstance(expected, String):
+        for value in expected:
+            if isinstance(value, (Sequence, String, Mapping)):
+                raise TypeError("Sequence contained a value that was not float or int")
         cls = ApproxSequence
     elif isinstance(expected, Decimal):
         cls = ApproxDecimal
diff --git a/changelog/3473.bugfix.rst b/changelog/3473.bugfix.rst
new file mode 100644
index 00000000000..508e63c08e8
--- /dev/null
+++ b/changelog/3473.bugfix.rst
@@ -0,0 +1,2 @@
+``pytest.approx`` does not handle strings, but this was not easily apparent so it now raises a ``TypeError`` when a string is passed in as the expected argument.
+``pytest.approx`` did not check all elements in a sequence to make sure they were valid type, a ``TypeError`` is now raised when an invalid element is in a sequence.
\ No newline at end of file
diff --git a/testing/python/approx.py b/testing/python/approx.py
index 9ca21bdf8e9..acd1aa3ef78 100644
--- a/testing/python/approx.py
+++ b/testing/python/approx.py
@@ -243,6 +243,10 @@ def test_int(self):
             assert approx(x, rel=5e-6, abs=0) == a
             assert approx(x, rel=5e-7, abs=0) != a
 
+    def test_string(self):
+        with pytest.raises(TypeError):
+            approx('abc')
+
     def test_decimal(self):
         within_1e6 = [
             (Decimal('1.000001'), Decimal('1.0')),