Osmolskae is a mid-sized dromaeosaurid, with adults measuring up to 2.07 m (6.8 ft) long, 0.5 m (1.6 ft) high at the hip, and weighing up to 15 kg (33 lb). The skull, which grows up to 25 cm (9.8 in) long, was uniquely up-curved, concave on the upper surface and convex on the lower. The jaws are lined with 26–28 widely spaced teeth on each side, each more strongly serrated on the back edge than the front. An adaptation that improves its ability to catch and hold fast-moving prey. Like other dromaeosaurids it has a large manus (‘hand’) with three strongly curved claws, which were similar in construction and flexibility to the wing bones of modern birds. The second digit was the longest of the three digits present, while the first was shortest.Osmolskae walk on only their third and fourth digits. The second digit, for which Osmolskae is most famous, was highly modified and held retracted off of the ground. It bore a relatively large, sickle-shaped claw. This enlarged claw, which could be over 6.5 cm (2.6 in) long around its outer edge, is a predatory device used to tear into prey, delivering fatal blows.
Osmolskae are pack hunting carnivores. Primarily they target herd animals, but they will go after just about any source of meat they can find.
Osmolskae males can be found alone, but most commonly Osmolskae are found in packs. Much like lions, the females are the most adept hunters within the group.