Background The aim of this study was to demonstrate the effect of surface electrical stimulation in a seated position (SESSP), as pelvic floor muscle (PFM) training, on PFM functions (time to reach maximal pressure [TRMP], muscle strength, power and endurance), urinary leakage and quality of life in patients with stress urinary incontinence (SUI).Methods Women with SUI were randomized into an SESSP group (n = 18) or control group (n = 18). Quality of life were assessed by the Incontinence Quality of Life Questionnaire (I-QOL). Ultra-short pad test results and PFM functions were measured by perineometer. Changes in the outcomes were assessed before and 8 weeks after SESSP training.Results Thirty-three participants were included in the analysis. There were significant differences in I-QOL (avoidance and limiting behaviors, psychosocial impacts, social embarrassment and total score) in between (SESSP vs. control group) and within (pre vs. post) group analyses. Significant increases in PFM strength, power, and endurance, and significant decreases in the TRMP and pad weight, were observed between (SESSP vs. control group) and within (pre vs. post) groups.Conclusion SESSP in a seated position can be recommended to improve QOL, urinary leakage, and PFM functions in SUI patients. Trial registration Current Controlled Trials KCT0003357 (the date of registration: 2018.11.16) and retrospectively registered.