Agroforestry systems can be an effective means of maintaining or even enhancing crop yields under climate change. In agroforestry, trees compete with crops for soil resources, but they can also improve the growing conditions of crops under drought by providing shade. They can promote higher crop yields and higher harvest quality. However, the beneficial effect of tree shade may depend on the seasonal pattern of rainfall which determines the compensation between yield components. In this study, we evaluated the production of two annual crops (durum wheat and faba bean) in olive agroforestry in northern Morocco. We manipulated water supply in a field experiment to span the high inter-annual rainfall variability at the site and tested whether olive trees reduce or improve crop yields. We assessed the effect of water addition on crop growth, yield components and final yields and estimated the land equivalent ratio of olive agroforestry. Agroforestry penalized crop growth and yield whatever the water regime. The number of grains per unit area was the most impacted yield component. However, agroforestry improved individual grain weight and the protein content of grains but not sufficiently to compensate for yield loss. Overall, we show that agroforestry systems are generally more land productive than sole crops and trees and we present examples of how changing water supply may impact the performance of olive agroforestry in a drier future.