diff --git a/ppb_vector/vector2.py b/ppb_vector/vector2.py
index 74b730bb..f80a7c5f 100644
--- a/ppb_vector/vector2.py
+++ b/ppb_vector/vector2.py
@@ -231,6 +231,9 @@ def isclose(self: VectorOrSub, other: VectorLike, *,
         For the values to be considered close, the difference between them
         must be smaller than at least one of the tolerances.
         """
+        if abs_tol < 0 or rel_tol < 0:
+            raise ValueError("Vector2.isclose takes non-negative tolerances")
+
         other = Vector2.convert(other)
 
         rel_length = max(
@@ -241,8 +244,8 @@ def isclose(self: VectorOrSub, other: VectorLike, *,
 
         diff = (self - other).length
         return (
-            diff < rel_tol * rel_length or
-            diff < float(abs_tol)
+            diff <= rel_tol * rel_length or
+            diff <= float(abs_tol)
         )
 
     @staticmethod
diff --git a/tests/test_vector2_isclose.py b/tests/test_vector2_isclose.py
new file mode 100644
index 00000000..ddc4eae8
--- /dev/null
+++ b/tests/test_vector2_isclose.py
@@ -0,0 +1,30 @@
+from ppb_vector import Vector2
+from pytest import raises # type: ignore
+from utils import units, vectors
+from hypothesis import assume, given, note, example
+from hypothesis.strategies import floats
+
+
+@given(x=vectors(), abs_tol=floats(min_value=0), rel_tol=floats(min_value=0))
+def test_isclose_to_self(x, abs_tol, rel_tol):
+    assert x.isclose(x, abs_tol=abs_tol, rel_tol=rel_tol)
+
+@given(x=vectors(max_magnitude=1e75), direction=units(),
+       abs_tol=floats(min_value=0, max_value=1e75))
+def test_isclose_abs_error(x, direction, abs_tol):
+    assert x.isclose(x + (1 - 1e-12) * abs_tol * direction, abs_tol=abs_tol, rel_tol=0)
+
+@given(x=vectors(), direction=units(),
+       rel_tol=floats(min_value=0, max_value=1e75))
+def test_isclose_rel_error(x, direction, rel_tol):
+    assert x.isclose(x + rel_tol * x.length * direction, abs_tol=0, rel_tol=rel_tol)
+
+
+def test_isclose_negative_tolerances():
+    zero = Vector2(0, 0)
+
+    with raises(ValueError):
+        zero.isclose(zero, abs_tol=-1)
+
+    with raises(ValueError):
+        zero.isclose(zero, rel_tol=-1)