In order to evaluate the results of pars plana vitrectomy (PPV) for the treatment of posteriorly dislocated intraocular lens (PC-IOL), we retrospectively examined and analyzed the hospital records of patients who had undergone PPV to exchange or reposition a PC-IOL dislocated into the vitreous cavity. Of 20 eyes in 20 patients, IOL exchange was performed in 6 eyes, and IOL repositioning in 14 eyes. Posteriorly dislocated IOL occurred in 14 eyes during or within 2 days, and in 6 eyes 6 months after the IOL implantation. Thirteen eyes were surgically treated early after the occurrence, within 3 days, while 7 eyes were treated later, between 5 to 7 days. Compared with preoperative best-corrected visual acuity, the final visual acuity improved more than 2 lines in 12 eyes. With no significant difference on the statistics, earlier visual rehabilitation seemed to be shown in late-treated patients than in early-treated. Accordingly, a posterior dislocation of IOL can be successfully treated with PPV, and barring any serious complications such as retinal detachment, there is no need for surgery immediately following the occurrence.