Cimbex femoratus can reach a length of 17–23 millimetres (0.67–0.91 in).

Larvae are pale bluish-green, about 45 mm long and they look very similar to caterpillars.

On the back they usually have a dark, narrow bluish longitudinal stripe.

They can be found between June and September and feed exclusively on leaves of birch (Betula sp.)

These sawflies prefer areas where birch trees can be found.