A 7-year-old girl was admitted to our clinic after crash injury with air gun pellet in her right eye. There was an intense anterior chamber reaction and hyphema on the biomicroscopic examination. During the control examination after treatment of hyphema including cyclopentolate 1%, prednisolone acetate 1% and lomefloxacin 0.3%, anisocoria and mydriasis in the right eye were observed and the difference between both pupils was less in darkness. The case was diagnosed as tonic pupil following trauma, and diluted pilocarpine 0.125% test was performed. On diluted pilocarpine test, right pupil responded excessively to pilocarpine compared with the other pupil. As in our case, in cases with anisocoria following blunt trauma to orbit, tonic pupil should be keep in mind.