Purpose To evaluate macular function before and after vitrectomy for idiopathic epiretinal membrane (ERM) with internal limiting membrane (ILM) peeling by multifocal electroretinography (mfERG) and their correlations with visual acuity (VA) and central subfoveal thickness (CST) by optical coherence tomography (OCT). Settings and Design A prospective interventional case series of 15 eyes with idiopathic ERM of 14 patients who underwent pars plana vitrectomy (PPV) for ERM removal with ILM peeling. Methods Multifocal electroretinography (mfERG) and OCT were performed preoperatively and one month after surgery. The response amplitude densities and implicit times of mfERG were analyzed. Correlation analyses among visual acuity, CST and mfERG values in the five concentric rings were performed. Results The first order responses of mfERG recorded preoperatively showed diffuse reduction in P1 amplitudes in all 5 rings with no statistically significant differences in mfERG responses after ERM surgery. Correlation coefficients showed a significant correlation between postoperative VA and P1 amplitude of ring 2 (P = 0.005). There was no significant correlation between postoperative CST and P1 amplitude for all rings Conclusions The mfERG responses in eyes with idiopathic ERM show macular function abnormalities and correlate with VA after surgery. The residual retinal distortion along with the damage to inner retinal layers and Muller cell dysfunction associated with ILM peeling affect the mfERG responses after surgery. The incorporation of mfERG into the pre- and post-operative assessment of patients with iERM, allow for identification of functional impairment and predict visual outcomes.