Highlights: • Water scarcity threatens the sustainability of Mediterranean rainfed agriculture. • Diversification as an adaptation of agriculture to water scarcity. • Field diversification can take the form of intercropping, agroforestry, and service crop. • Diversifying crops (number, abundance, and spatial organization) in landscapes. • Building small-scale WHI in landscapes. Abstract: Rainfed Mediterranean agriculture (MA) must adapt to water scarcity due to climate change and pressures on water resources. According to recent literature, two adaptation solutions based on the concept of diversification can be explored. The first solution is crop diversification at the field level. Three main cropping systems, namely agroforestry, intercropping, and service crops, have been shown to increase soil water availability and to improve crop water use. The second solution is to consider diversification at the landscape level by diversifying crops and associated agricultural management practices (in number, abundance, and spatial organization) and building small-scale water-harvesting infrastructures (WHI). In order to move toward a sustainable MA, one of the main scientific challenges ahead is to provide knowledge and tools, such as integrated agro-hydrological models, useful to evaluate several spatiotemporal combinations of these solutions in order to optimize soil water availability and crop water use.