Various instruments are used to evaluate the severity of stress urinary incontinence (SUI) in clinical trials for SUI surgery. We conducted a scoping review with the primary aim of investigating the use of such instruments. A comprehensive search in PubMed/MEDLINE, Cochrane Library, ClinicalTrials.gov, and WHO ICTRP was carried out. Inclusion criteria were studies including patients undergoing surgical intervention for SUI with assessment of SUI severity performed pre- and post-operatively. Exclusion criteria were nonprospective studies, nonrandomized studies, studies not in the English language, and the absence of reporting the methods of SUI severity evaluation in the study. In total, 8,886 articles were identified, yielding 100 papers for data extraction. The most frequent interventions were mid-urethral slings (85 studies), Burch colposuspension (10 studies), and the use of bulking agents (3 studies). The most frequently used instruments for objective evaluation of SUI were urodynamics (90 studies), nonvalidated cough stress test (83 studies), and 1-h pad test (28 studies). The most frequently used instruments for subjective evaluation were bladder diary (37 studies), Incontinence Impact Questionnaire-7 (26 studies), and Urinary Distress Inventory-6 (23 studies). There were three studies reporting results according to the severity of pre- and post-operative SUI. There is significant heterogeneity regarding the instruments used to evaluate the severity of SUI in surgical trials for female incontinence. There is a paucity of data regarding results according to the pre-operative severity of SUI. Hence, commonly agreed standardized methods for the assessment of SUI severity are needed to improve comparability between clinical trials for SUI surgery.