(1) Background: Sexual function can be affected up to and beyond 18 months postpartum, with some studies suggesting that spontaneous vaginal birth results in less sexual dysfunction. This review examined the impact of mode of birth on sexual function in the medium- (≥6 months and <12 months postpartum) and longer-term (≥12 months postpartum). (2) Methods: Literature published after January 2000 were identified in PubMed, Embase and CINAHL. Studies that compared at least two modes of birth and used valid sexual function measures were included. Systematic reviews, unpublished articles, protocols and articles not written in English were excluded. Quality was assessed using the Newcastle Ottawa Scale. (3) Results: In the medium-term, assisted vaginal birth and vaginal birth with episiotomy were associated with worse sexual function, compared to caesarean section. In the longer-term, assisted vaginal birth was associated with worse sexual function, compared with spontaneous vaginal birth and caesarean section; and planned caesarean section was associated with worse sexual function in several domains, compared to spontaneous vaginal birth. (4) Conclusions: Sexual function, in the medium- and longer-term, can be affected by mode of birth. Women should be encouraged to seek support should their sexual function be affected after birth.