To evaluate the effect of preoperative pelvic floor muscle training (PFMT) on pelvic floor muscle (PFM) contraction, symptoms of pelvic organ prolapse (POP) and anatomical POP, 6 months after prolapse surgery, and to assess the overall changes in PFM contraction, POP symptoms and pelvic organ descent after surgery. This was a randomized controlled trial of 159 women with symptomatic POP, Stage 2 or higher, scheduled for surgery. Participants were randomized to intervention including daily PFMT from inclusion to surgery (n = 81) or no intervention (controls; n = 78). Participants were examined at inclusion, on the day of surgery and 6 months after surgery. PFM contraction was assessed by: vaginal palpation using the Modified Oxford scale (MOS; 0-5); transperineal ultrasound, measuring the percentage change in levator hiatal anteroposterior diameter (APD) from rest to maximum PFM contraction; vaginal manometry; and surface electromyography (EMG). POP distance from the hymen in the compartment with the most dominant prolapse and organ descent in the anterior, central and posterior compartments were measured on maximum Valsalva maneuver. POP symptoms were assessed based on the sensation of vaginal bulge, which was graded using a visual analog scale (VAS; 0-100 mm). Linear mixed models were used to assess the effect of PFMT on outcome variables. Of the 159 women randomized, 151 completed the study, comprising 75 in the intervention and 76 in the control group. Mean waiting time for surgery was 22 ± 9.7 weeks and follow-up was performed on average 28 ± 7.8 weeks after surgery. Postoperatively, no difference was found between the intervention and control groups with respect to PFM contraction assessed by vaginal palpation (MOS, 2.4 vs 2.2; P = 0.101), manometry (19.4 vs 19.7 cmH2 O; P = 0.793), surface EMG (33.5 vs 33.1 mV; P = 0.815) and ultrasound (change in hiatal APD, 20.9% vs 19.3%; P = 0.211). Furthermore, no difference between groups was found for sensation of vaginal bulge (VAS, 7.4 vs 6.0 mm; P = 0.598), POP distance from the hymen in the dominant prolapse compartment (-1.8 vs -2.0 cm; P = 0.556) and sonographic descent of the bladder (0.5 vs 0.8 cm; P = 0.058), cervix (-1.3 vs -1.1 cm; P = 0.569) and rectal ampulla (0.3 vs 0.4 cm; P = 0.434). In all patients, compared with findings at initial examination, muscle contraction improved after surgery, as assessed by palpation (MOS, 2.1 vs 2.3; P = 0.007) and ultrasound (change in hiatal APD, 17.5% vs 20.1%; P = 0.001), and sensation of vaginal bulge was reduced (VAS, 57.6 vs 6.7 mm; P < 0.001). In addition, compared with the baseline examination, POP distance from the hymen in the dominant prolapse compartment (1.9 vs -1.9 cm; P < 0.001) and sonographic descent of the bladder (1.3 vs 0.6 cm; P < 0.001), cervix (0.0 vs -1.2 cm; P < 0.001) and rectal ampulla (0.9 vs 0.4 cm; P = 0.001) were reduced. We found no effect of preoperative PFMT on PFM contraction, POP symptoms or anatomical prolapse after surgery. In all patients, PFM contraction and POP symptoms were improved at the 6-month follow-up, most likely due to the anatomical correction of POP. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.