In electroconvulsive therapy (ECT), remifentanil is often used concurrently with anesthetics. The objective of this study was to provide an up-to-date and comprehensive review on how the addition of remifentanil to anesthetics affects seizure duration and circulatory dynamics in mECT. We performed a meta-analysis of RCTs that investigated seizure duration and circulatory dynamics in patients treated with ECT using anesthetics alone (non-remifentanil group) and with anesthetics plus remifentanil (remifentanil group). A total of 13 RCTs (380 patients and 1024 ECT sessions) were included. The remifentanil group showed a significantly prolonged seizure duration during ECT compared to the non-remifentanil group [motor: 9 studies, SMD = 1.25, 95 % CI (0.21, 2.29), p = 0.02; electroencephalogram: 8 studies, SMD = 0.98, 95 % CI (0.14, 1.82), p = 0.02]. The maximum systolic blood pressure (SBP) was significantly reduced in the remifentanil group compared to the non-remifentanil group [7 studies, SMD = -0.36, 95 % CI (-0.65, 0.07), p = 0.02]. Substantial heterogeneity was observed for meta-analyses for seizure durations, but a pre-planned subgroup analysis revealed that seizure duration was prolonged only when the use of the anesthetic dose was reduced in the remifentanil group. The results of our study suggest that addition of remifentanil to anesthesia in ECT may lead to prolonged seizure duration when it allows the use of reduced anesthetic doses. Further, the addition of remifentanil was associated with reduced maximum SBP.