Low crop production and food insecurity faced by smallholder farmers have been caused by climate change, which encourages high temperatures, soil moisture, and nutrient stress. To mitigate these climate change constraints, smallholder farmers in semiarid areas can adopt climate-smart agricultural practices to lengthen the growing season; conserve soil and water, such as rainwater harvesting (RWH) and integrated nutrient management (INM); and improve crop yields. INM is an approach used to enhance soil fertility and plant nutrition using organic and inorganic nutrient sources in a balanced and efficient manner to enhance crop productivity and soil health while minimizing environmental impact. Therefore, the chapter’s objective is to explore the effects of rainwater harvesting and INM as a climate approach to achieve sustainable agriculture in selected African countries. The study used a systematic review to gather recently published articles on RWH and INM to mitigate climate change. Various cases from various countries were used to support the effects of RWH and INM on achieving sustainable agriculture. Smallholder farmers in semiarid areas of Kenya, Zimbabwe, Ethiopia, Tanzania, and Sudan adopted rainwater harvesting techniques such as tied ridges and planting pits, which increase crop yield with a minimum of 300 kg ha−1. Tied ridge proved to be one of the best RWH techniques in semiarid areas, which increase crop yield by 1841 kg ha−1 (maize) and 2156 kg ha−1 (sorghum) compared with tied contour, planting, and infiltration pits. The use of INM of organic and mineral fertilizer has the potential to reduce greenhouse gas emissions and increase water retention. Combining animal manure, agroforestry biomass, compost, and minimal mineral fertilizer improves soil health and increases carbon sequestration and crop yields. Farmers can integrate RWH and INM to improve soil water content, nutrients, and water availability. This integration has been noted to increase crop yields by 50–400% in semiarid areas. Ideally, the integration of RWH and INM will lengthen the growing season and improve soil water retention due to the high total porosity facilitated by INM. The combination has great potential in achieving sustainable agriculture in semiarid areas, with the integration of tied ridge and INM being the best in sandy clay loam and tied contours in sandy loam soils.