Background: Marital satisfaction is defined as a mental state reflecting the pressures and benefits perceived by the couple in their life. Several factors seem to contribute to marital satisfaction and success including having children. Objectives: The present study aimed at evaluating the effect of the number and gender composition of children (having only sons, only daughters, and children of both genders) on marital satisfaction in women of childbearing age in Tehran. Methods: This descriptive correlational study was conducted on 213 married females aged 15 to 45 years presenting to health centers in Tehran, Iran, in 2015. The demographic questionnaire, the ENRICH marital satisfaction scale, and a researcher-made childbearing questionnaire were used for data collection. Data were analyzed using descriptive statistics (mean and standard deviation) and ANOVA in SPSS version 17. The level of statistical significance was set at P < 0.05. Results: The results of the present study revealed a significant correlation between the mean score of marital satisfaction and the number of children (P = 0.005); for instance, women’s marital satisfaction reduced with an increase in the number of children. The results also revealed a greater marital satisfaction in women with children of the same gender than in those with children of both genders. Moreover, the mean score of marital satisfaction was significantly higher in women with only sons than in those with either only daughters or with children of both genders (P = 0.013). Conclusions: Women’s marital satisfaction decreased with an increase in the number of children. Children’s gender affected marital satisfaction. Women with only sons had a greater marital satisfaction than those women with only daughters, or with children of both genders.