Developing cultivars with adaptive traits to improve sustainability in the face of climate change is an important option for climate smart agriculture. The CROPGRO-cotton model was calibrated and evaluated at two locations in Cameroon over a period of two years using two planting dates and four contrasted cultivars. The model was used to assess yield gains by modifying plant traits such as specific leaf area, photosynthetic capacity and crop phenology. The ideotype was tested in conventional and conservation agriculture systems and under baseline and future climate conditions. The results revealed that, compared to existing cultivars, the ideotype requires longer to reach maturity and has thicker leaves with good photosynthetic capacity. In 2050 in North Cameroon, climate change will shorten time to maturity and cause a shift in the rainy season but neither change will have an effect on yields. Simulations with an ensemble of climate models revealed that models that assume higher rainfall predicted lower yields, suggesting that N leaching is a more important constraint than drought in North Cameroon. Our results will help cotton breeders select promising new traits to introduce in their cultivars for adaptation to climate changes in Cameroon and to similar sub-Saharan soil, cropping systems and climatic conditions.