Cereal production systems in semi-arid environments in Senegal are extensive and highly depend on weather and climate-related effects. Assessing climate change impacts on the main staple food crops is essential to ensure food security. This study aims to assess climate change impacts on millet and sorghum in Niakhar and Toubacouta, two locations in the Senegalese groundnut basin. Field experiment and climate data from RCP4.5 and RCP8.5 greenhouse gas concentration pathways were used to simulate future crop yield and growth cycle length. For each crop, two varieties were considered, a short (90 days) and a long (120 days) maturation cycle. Projections made using the SARRA–O model showed a downward trend of crop yield for all considered varieties and scenarios. These results were, however, more pronounced for the short-cycle variety. In addition, the short-cycle variety showed greater variability in yield trends with larger confidence intervals. In Niakhar, millet and sorghum yield loss for short duration is estimated around 30% by 2050, while the long-cycle variety yield gap was less than 20% compared to the reference period yield (1976–2005). Millet and sorghum yield reduction by 2050 is less pronounced in Toubacouta with around 20%. A slight relationship was inferred between rainfall and yield change, whereas a significant negative linear relationship was inferred between temperature and yield change. The future impact of climate change on these cereals would be mainly a loss of yield induced by rising temperatures. Thus, a thorough consideration of temperature effects will be essential for better adapting cereal production to future climatic conditions.