We aimed to evaluate the safety and efficacy of periurethral hypertonic saline (10% NaCl) injection in the treatment of stress urinary incontinence (SUI) and stress-predominant mixed urinary incontinence (S-MUI) in women. This was a prospective study conducted between January 2014 and April 2018 with 64 women (44 SUI and 21 S-MUI). Patients with SUI and S-MUI were evaluated using the Urinary Distress Inventory 6. Quality of life was evaluated with the Incontinence Quality of Life Scale and lower urinary tract symptoms of the women were evaluated with the International Consultation on Incontinence Questionnaire Female Lower Urinary Tract Symptoms Modules. Incontinence status and treatment success were assessed via the Stamey incontinence grade and pad test. The subjective success rate was 58.5%, and the objective success rate was 81.5%. The rate of reinjection was 21.5%, and the mean duration of reinjection was 8.92 months (3-19 months). Minor adverse effects were observed in 30.4% of the 79 injections. International Consultation on Incontinence Questionnaire Female Lower Urinary Tract Symptoms Modules and Incontinence Quality of Life Scale scores improved remarkably starting from the first month. Urinary Distress Inventory 6 scores in the S-MUI group also improved. The results indicate that hypertonic saline injection is an effective and safe method in the treatment of SUI and S-MUI. Since hypertonic saline is a much cheaper and more accessible substance compared to bulking agents, it seems to be a viable alternative for urinary incontinence treatment in women.