Pyxicephalus obbianus is a large ranid frog very similar to Pyxicephalus adspersus. P. obbianus adult specimens (larger than 90 mm) can be distinguished from P. adspersus by the size and placement of the tympanum. In P. obbianus, the tympanum is larger than the eye and lies very close to it. In P. adspersus, on the other hand, the tympanum is smaller than the eye and is separated from it by a distance larger than the tympanum itself.

P. obbianus adult specimens also generally seem to lack the vertebral light stripe found on most P. adspersus. According to Balletto et al. (1978), all the specimens of Pyxicephalus obbianus they examined that were larger then 23 mm (snout-urostyle) lacked the vertebral light stripe that was present in all of the specimens of Pyxicephalus adspersus that they examined but one. However, this cannot be used as a definite means of identification.