Women’s knowledge and conservation of agrobiodiversity are under-valued and less documented and recognized in the scientific spheres regardless of the variation in the local knowledge system. This study assessed the role of women and men in agricultural practices like land preparation, cultivation, processing and marketing as well as their contribution to farm diversification in the case of smallholder farmers in the Sinana district. We hypothesized that women’s involvement in different agricultural activities increases crop diversity on the farmlands and enhances agrobiodiversity practices in the area. We used primary data which was collected through household surveys, focus group discussions, and field observation. The results indicated there is a significant variation (p < 0.05) between women’s and men’s participation in the agricultural practice in the study area. Moreover, we found higher crop diversity in women-managed farmlands than in men-managed farmlands. This might be because women tend to use crops in a greater range of ways like seed management and in maintaining nutritional dietary and food security of the family. Moreover, the presence of off-farm male wage labor negatively influences the types and number of crops grown by men. Indeed, women farmers are a greater source of labor input in the different agricultural activities. They play a crucial role in farm diversification, conservation of agrobiodiversity, and ecological sustainability in the study area and elsewhere with similar environmental and socio-cultural settings.