The interior is relatively featureless with a small floor, with mounds of material deposited along the edges of the sloping inner walls.

To the north of the crater, along the edge of the highland peninsula between the two maria is a domed mountainous rise that is designated Mons Gruithuisen Gamma (γ).

Just to the east of this feature is another mountainous rise named Mons Gruithuisen Delta (δ).

Northwest of Gruithuisen crater is concentrated cluster of several craterlets, which was most likely formed from a single body that broke up just prior to impact.

By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Gruithuisen.