Macrophya montana can reach a length of 8-12mm. This species shows an evident sexual dimorphism.
The females are recognisable by black and yellow markings. The head is black with yellow clypeus and labrum. On the abdomen the first tergite is completely yellow, the fifth and sixth are broad, yellow, interrupted in the middle. On the seventh, sometimes also on the fourth, there are small yellow spots on the sides. Also the ninth tergite is yellow. These
markings are absent on the abdomen of the males, that are completely black.
In the females the legs are predominantly yellow with black markings. In the males the first two pairs of legs are pale yellow, while the hind legs are mainly black, but the tips of the tibias and part of tarsi are white.