To investigate posterior vitreous detachment (PVD) and pars plana vitrectomy (PPV) effects on contrast sensitivity function (CSF) in patients with a multifocal intraocular lens (MfIOL). This single-center prospective case-control study analyzed 27 patients with 43 consecutive eyes. Twenty patients with 36 consecutive eyes received MfIOL implantation with either ZLB00 or ZMB00. CSF was measured as the area under the log contrast sensitivity function (AULCSF) in the presence and absence of PVD (PVD+ group and PVD− group, respectively). Seven eyes associated with a symptomatic PVD and severe visual dissatisfaction after MfIOL implantation underwent PPV (symptomatic PVD+ group). CSF was measured prior to and after PPV. The mean AULCSF was significantly lower in the PVD+ group (1.5 ± 0.1) versus the PVD− group (1.7 ± 0.1, p < 0.0001). Major complaints in the symptomatic PVD+ group included floaters (n = 2) and blurry vision (n = 5). The preoperative AULCSF (1.4 ± 0.1) was significantly lower in the symptomatic PVD+ group versus the PVD− group (p < 0.0001) and PVD+ group (p = 0.02). The preoperative AULCSF in the symptomatic PVD+ group was significantly improved after PPV (1.4 vs. 1.7, respectively, p = 0.002). PVD significantly decreased CSF in patients with MfIOL. Patients with symptomatic PVD exhibited the greatest decrease in CSF, which was significantly improved after PPV. Measurement of CSF and careful assessment of PVD may be useful in determining the appropriateness of surgical intervention for improving visual performance and satisfaction in MfIOL patients with symptomatic PVD.