The problem of inadequate basic sanitation services to women living in informal settlement is a serious public health concern. Access to basic sanitation services is still a challenge in informal settlements and sanitation needs of some groups specifically women at times remain unmet. This study assessed the utilization of sanitation facilities by women in respect to design parameters, socio-economic factors, and operation and maintenance aspects in Mukuru Kwa Reuben, Kenya. The objectives of the study were; to assess the influence of design parameters on the utilization of sanitation facilities by women in Mukuru Kwa Reuben, to examine the influence of socioeconomic factors on the utilization of sanitation facilities by women in Mukuru Kwa Reuben, and to investigate the influence of operation and maintenance on the utilization of sanitation facilities by women in Mukuru Kwa Reuben. The study was premised on the Health Action Process Approach. The study targeted all women aged 18 and above who consent and are the primary users of sanitation facilities and resident in Mukuru Kwa Reuben community. Sample for the study was 395 gotten using the Yamane formula. Sampling was by use of clustered simple random sampling for women in households. The main instruments of data collection were, questionnaire, focus group discussions, and observation. Quantitative data was analyzed for descriptive and inferencial statistics and findings presented in form of percentages, means, and frequencies then presented in tables. Qualitative data was analysed thematically presented in form of narratives. Results from the analysis showed that majority of the respondents (54.2%) were aged 31-40 years, married (41.0%), attained primary level education (49.0%), and employed (35.4%). The most common sanitation facility was container based (51.0%). Correlation results showed that design of floors, walls, and roofs (r=0.442, p=0.000), indicating a moderate positive association with utilization, handwashing facilities (r=0.219, p=0.000), indicating a weak positive association with utilization, distance to facility (r=0.696, p=0.000), indicating a strong positive association with utilization, beliefs (r=-0.613, p=0.000), indicating a strong negative association with utilization, education level (r=0.593, p=0.000), indicating a strong positive association with utilization, economic status (r=0.466, p=0.000), indicating a moderate positive association with utilization, cleaning frequency (r=0.672, p=0.000), indicating a strong positive association with utilization, exhausting frequency (r=0.319, p=0.000), indicating a moderate positive association with utilization, repairing (r=0.191, p=0.000), indicating a weak positive association with utilization, and daily inspection (r=0.364, p=0.000) indicating a moderate positive association with utilization. It is concluded that design parameters, socioeconomic factors, and operations and maintenance all have a positive association with utilization of sanitation facilities. The study recommends that efforts should be made to ensure that sanitation facilities are easily accessible and located within reasonable proximity to residential areas. This can involve establishing more facilities in underserved areas or implementing strategies to reduce travel distances.