diff --git a/pyiceberg/expressions/visitors.py b/pyiceberg/expressions/visitors.py
index 320cd3110e..d835d0d4c5 100644
--- a/pyiceberg/expressions/visitors.py
+++ b/pyiceberg/expressions/visitors.py
@@ -1852,10 +1852,10 @@ def visit_is_nan(self, term: BoundTerm) -> BooleanExpression:
 
     def visit_not_nan(self, term: BoundTerm) -> BooleanExpression:
         val = term.eval(self.struct)
-        if isinstance(val, SupportsFloat) and not math.isnan(val):
-            return self.visit_true()
-        else:
+        if isinstance(val, SupportsFloat) and math.isnan(val):
             return self.visit_false()
+        else:
+            return self.visit_true()
 
     def visit_less_than(self, term: BoundTerm, literal: LiteralValue) -> BooleanExpression:
         if term.eval(self.struct) < literal.value:
diff --git a/tests/expressions/test_residual_evaluator.py b/tests/expressions/test_residual_evaluator.py
index 375639ee7b..29dbfcea8d 100644
--- a/tests/expressions/test_residual_evaluator.py
+++ b/tests/expressions/test_residual_evaluator.py
@@ -211,7 +211,7 @@ def test_is_not_nan() -> None:
     res_eval = residual_evaluator_of(spec=spec, expr=predicate, case_sensitive=True, schema=schema)
 
     residual = res_eval.residual_for(Record(None))
-    assert residual == AlwaysFalse()
+    assert residual == AlwaysTrue()
 
     residual = res_eval.residual_for(Record(2))
     assert residual == AlwaysTrue()
@@ -223,7 +223,7 @@ def test_is_not_nan() -> None:
     res_eval = residual_evaluator_of(spec=spec, expr=predicate, case_sensitive=True, schema=schema)
 
     residual = res_eval.residual_for(Record(None))
-    assert residual == AlwaysFalse()
+    assert residual == AlwaysTrue()
 
     residual = res_eval.residual_for(Record(2))
     assert residual == AlwaysTrue()