Introduction and hypothesis Pelvic floor muscle weakness is a common cause of pelvic organ prolapse and urinary incontinence. Surgical repair of prolapse is commonly undertaken; however, the impact on pelvic floor muscle tone is unknown. The aim of this study was to compare the effect of anterior and posterior colporrhaphy on pelvic floor activation. Methods Patients aged under 70 undergoing primary anterior or posterior colporrhaphy were recruited. Intra-vaginal pressure was measured at rest and during pelvic floor contraction using the Femfit® device (an intra-vaginal pressure sensor device IVPSD). Peak pressure and mean pressure over 3 s were measured in millimetres of mercury. The pre- and post-operative measurements were compared. The difference between the means was assessed using Cohen’s D test, with significance set at p <0.05 Results A total of 37 patients completed pre- and post-operative analysis, 25 in the anterior colporrhaphy group and 12 in the posterior colporrhaphy group. Anterior colporrhaphy showed no significant change in pelvic floor tone. Change in peak pressure was −1.71mmHg (−5.75 to 2.33; p =0.16) and change in mean pressure was −0.86 mmHg (−4.38 to 2.66; p =0.31). Posterior colporrhaphy showed a significant increase in peak pelvic floor muscle tone of 7.2 mmHg (0.82 to 13.58; p =0.005) and mean pressure of 4.19 mmHg (−0.09 to 8.47; p =0.016). Conclusions Posterior colporrhaphy significantly improves pelvic floor muscle tone, whereas anterior colporrhaphy does not. Improved understanding of the impact of pelvic floor surgery may guide future management options for other pelvic floor disorders. Further work is needed to confirm the association of this improvement in pelvic floor disorders.