OBJECTIVES: To present the characteristics of women attending a tertiary urogynecology pelvic floor scan clinic with mid-urethral sling (MUS) complications and examine the association between patient symptoms and findings on two-dimensional (2D) perineal and three-dimensional (3D) endovaginal ultrasound. METHODS: This was a cross-sectional study of all women with MUS complications referred to a specialist pelvic floor ultrasound clinic between October 2016 and October 2018. Detailed history was obtained regarding their symptoms and time of onset. All patients underwent 2D perineal and 3D endovaginal ultrasound assessment. The association between patient symptoms and ultrasound findings was evaluated using logistic regression analysis. Only symptomatic women with a single MUS, without other pelvic floor mesh, prior mesh excision or bulking agents, were included in the regression analysis. RESULTS: A total of 311 women with a history of MUS surgery were seen during the study period. Vaginal and/or non-vaginal pain was reported by 80% of patients and this was the primary presenting complaint in 59% of the patients. One-third of the patients reported symptoms starting within 4 weeks after surgery. The data of 172 patients were included in the regression analysis. MUS position within the rhabdosphincter was significantly associated with voiding dysfunction (odds ratio (OR), 10.6 (95% CI, 2.2-50.9); P = 0.003). Voiding dysfunction was highest in those with C-shaped MUS both at rest and on Valsalva maneuver (OR, 3.2 (95% CI, 1.3-7.6); P < 0.001). MUS position in the distal third of the urethra was significantly associated with a higher rate of recurrent urinary tract infection (OR, 2.9 (95% CI, 1.3-6.3); P = 0.01). CONCLUSIONS: Pelvic floor ultrasound can provide insight into the position and shape of the MUS, which could explain some patient symptoms and guide management or surgical planning. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.