Heliophanus cupreus can reach a body length of about 3.6–4 mm (0.14–0.16 in) in males, of 4.6–5.8 mm (0.18–0.23 in) in females. These spiders have a dark, blackish body, with a metallic sheen. On the female the pedipalps are yellow or light brown and contrast with her overall appearance. Furthermore the prosoma is usually crossed by a white line behind the eyes and the abdomen is circled with a white line, with white dots
above.
The male has dark palps with white squamose hairs on front. The tibial apophysis has a fine, long, pointed, hook-shaped process. The male has a long palpal bulb. The cephalothorax is black with a metallic sheen and has white hairs, towards the front bright and on some individuals there are 1-2 bright pairs of spots to the rear.
Legs are light yellow, with black longitudinal stripes, although some individuals may have uniformly dark legs. The
opisthosoma is grey-black, again with a metallic sheen and white hairs.