Introduction and hypothesis The literature presents controversial results regarding the role of delivery mode in pelvic floor muscle (PFM) function after birth. Some studies showed a greater impairment of PFM function after vaginal delivery compared with cesarean section, while others have not identified a significant difference between these two modes of delivery. This study aimed to investigate whether there was a difference in short-term PFM function after childbirth in primiparous women who underwent cesarean section compared with those who underwent vaginal delivery. Methods Up to December 2018, the PubMed-MEDLINE, CINAHL, Embase, Bireme, Scopus, Web of Science, and Science Direct databases were searched. Two independent reviewers performed the selection process based on titles, abstracts, and full-text reading. Observational studies comparing PFM function after cesarean section versus vaginal delivery in primiparous women were included. PRISMA guidelines and Cochrane recommendations were followed. Methodological quality of the primary studies was assessed through the checklist proposed by the Joanna Briggs Institute for cross-sectional studies. Random effects meta-analysis was performed to synthesize evidence regarding PFM strength in primiparous woman after vaginal delivery compared with cesarean section. The GRADE approach was applied to classify the quality of the evidence. Results Eleven studies met the inclusion criteria and were included in this review. A total of 1726 primiparous women were analyzed after childbirth. Five studies were included in the meta-analysis. No difference in PFM strength after childbirth was identified when cesarean section was compared with vaginal delivery standardized mean difference (SMD): −0.15, 95% confidence interval (CI): −0.85 to 0.56. Differences in PFM strength were identified when patients who underwent cesarean section were compared with those with an episiotomy or instrumented vaginal delivery (SMD: −12.51, CI 95%: −24.57 to −0.44), favoring the cesarean section group. In both cases, the quality of evidence was classified as very low because of the observational design of the included studies and population heterogeneity. Conclusion There was no difference in short-term PFM strength after childbirth between primiparous women who underwent cesarean section or vaginal delivery, as assessed through vaginal manometry. However, we identified reduced PFM strength in women who underwent an episiotomy or instrumented vaginal delivery compared with those who underwent cesarean section. Nevertheless, this conclusion should be cautiously considered as the observational design of the primary studies and possible heterogeneity among the primiparous women included in the studies contributed to reducing the quality of the evidence synthesized. Future primary studies with longitudinal designs and long-term follow-up periods are needed to strengthen the quality of evidence and provide more conclusive evidence to guide clinical practice.