The autonomy of women in sexual and reproductive decision-making within family settings may represent gender equality and reproductive health relief. The theory of gender and power was used to identify socio-economic factors that influence women’s decision-making on sex and family size. A survey of 568 married and cohabiting women was conducted in Mahikeng, South Africa in 2012. Structured questionnaires were used in data collection and were analysed using descriptive statistics and binary logistic regression methods. The Findings of the study revealed 60.7% and 70.1% women participate in decisions on sex and on size of family respectively. Perceptions husbands had the right to sex, experience sexual violence, being in religious and traditional unions had negative impacts on women’s sexual autonomy. Employed women and reporting choosing of partners significantly enhanced women’s sexual autonomy. Traditional union, experienced of sexual violence sex, perceptions that husbands had right to sex, increasing age, and number of living children significantly reduced women’s decision-making autonomy on family size. The findings partially validated the sexual division of constructs of labour and power in the theory of gender and power. We recommend that women need to be empowered socially and economically to decide freely on sex and family size as indicators of sexual and reproductive health.