Introduction: menopause causes clinical symptoms that significantly impact women’s quality of life. Phytoestrogens, such as soy isoflavones, have been studied as treatment for climacteric syndrome, showing improvements in vasomotor and psychological symptoms.Objective: to determine the impact of the use of phytoestrogens (soy isoflavones) on the quality of life of women with perimenopause or postmenopause at Family Medicine Unit No. 55 of the Mexican Social Security Institute in Culiacán, Sinaloa, Mexico. Method: a randomized clinical trial was conducted with 44 women aged 45 to 60 with climacteric symptoms. Participants were assigned to an experimental group (EG), which received 50 mg of soy isoflavones every 24 hours, and a control group (CG), which received a placebo for 12 weeks. The Menopause Rating Scale was applied before and after the intervention to evaluate somatic, psychological, and urogenital symptoms. Descriptive and inferential statistics were used. Results: supplementation with soy isoflavones in the EG showed significant improvements in overall quality of life (Cohen d = 1,54), as well as in the somatic (d = 1,52) and psychological (d = 1,10) subscales, indicating a large effect (d > 0,80). However, the urogenital dimension showed no significant effect (d = 0). The CG experienced a significant deterioration in these subscales. Conclusions: soy isoflavones significantly improved the quality of life of women in perimenopause and postmenopause in the somatic and psychological dimensions, showing a large effect. No changes were observed in the urogenital dimension