Dwarf crocodiles attain a medium adult length of 1.5 m (4.9 ft), though the maximum recorded length for this species is 1.9 m (6.2 ft).
Adult specimens typically weigh between 18 and 32 kg (40 and 71 lb), with the largest females weighing up to 40 kg (88 lb) and the largest males weighing 80 kg (180 lb).
This makes it the smallest living crocodile species, although the Cuvier's dwarf caiman (Paleosuchus palpebrosus), a member of the family Alligatoridae, is smaller at up to about 1.7 m (5.6 ft).
If the Congo dwarf crocodile (O. osborni) is recognized as a valid species, it would be both the smallest crocodile and the smallest crocodilian since it does not surpass 1.2 m (3.9 ft).
Adults are all dark above and on their sides, while the underside is yellowish with black patches.
Individuals living in caves may have orange patches, apparently due to alkaline bat guano that erodes the skin of the crocodile.
Juveniles have a lighter brown banding on body and tails and yellow patterns on the head.

As a result of its small size and heightened vulnerability to predation, this species of crocodile has a heavily armoured neck, back, and tail and also has osteoderms on its belly and underside of neck.

Osteolaemus has a blunt short snout, as long as it is wide, similar to that of a Cuvier's dwarf caiman, probably a result of occupying a similar ecological niche.
The dentition consists of four premaxillary teeth, 12 to 13 on the maxilla, and 14 to 15 on the dentary bone.

O. t. tetraspis has lighter colours, a more pointed, upturned snout, and more body armour than O. t. osborni.
Dwarf crocodiles attain a medium adult length of 1.5 m (4.9 ft), though the maximum recorded length for this species is 1.9 m (6.2 ft). Adult specimens typically weigh between 18 and 32 kg (40 and 71 lb), with the largest females weighing up to 40 kg (88 lb) and the largest males weighing 80 kg (180 lb). This makes it the smallest living crocodile species, although the Cuvier's dwarf caiman (Paleosuchus palpebrosus), a member of the family Alligatoridae, is smaller at up to about 1.7 m (5.6 ft). If the Congo dwarf crocodile (O. osborni) is recognized as a valid species, it would be both the smallest crocodile and the smallest crocodilian since it does not surpass 1.2 m (3.9 ft). Adults are all dark above and on their sides, while the underside is yellowish with black patches. Individuals living in caves may have orange patches, apparently due to alkaline bat guano that erodes the skin of the crocodile. Juveniles have a lighter brown banding on body and tails and yellow patterns on the head.
As a result of its small size and heightened vulnerability to predation, this species of crocodile has a heavily armoured neck, back, and tail and also has osteoderms on its belly and underside of neck.
Osteolaemus has a blunt short snout, as long as it is wide, similar to that of a Cuvier's dwarf caiman, probably a result of occupying a similar ecological niche. The dentition consists of four premaxillary teeth, 12 to 13 on the maxilla, and 14 to 15 on the dentary bone.
O. t. tetraspis has lighter colours, a more pointed, upturned snout, and more body armour than O. t. osborni.
Dwarf crocodile