The diversified cropping systems has several positive effects in environmental and economic terms, and even is a validated way to mitigate the effects of climate change. However, there is no certainty about their effect on the main crop water status, especially in areas where water scarcity is almost permanent, as in SE Spain. Therefore, our objective was to evaluate the effect of incorporating two different diversified cropping systems in a monoculture (MC) of mandarin trees on its water status and yield under moderate and severe water scarcity conditions. Six treatments based on different crop diversifications were tested under two differential irrigation treatments on mandarin trees for three consecutive years: (i) a mandarin monoculture control treatment (MC-CTL), with permanent bare alleys and irrigated at ~70% ETc during the whole season; (ii) a diversified mandarin crop (D1-CTL), irrigated as MC-CTL, with a rotation of fava bean and barley/vetch in the alleys; and (iii) a second diversified mandarin crop (D2-CTL), irrigated as MC-CTL, with an seasonal rotation of fava bean, purslane and cowpea. Additionally, three regulated deficit irrigation (RDI) treatments were evaluated, denoted as (iv) MC-RDI, (v) D1-RDI and (vi) D2-RDI, irrigated as MC-CTL, except during the fruit growth period, when it was reduced by 50% with respect to this treatment and with an irrigation threshold of a midday stem water potential of ~ –1.5 MPa. The mandarin yield was not affected by the effect of diversifications, but the RDI regime reduced it by 30.1% with respect to CTL treatment. Alley cropping on D1 was established before and after the period of maximum water requirement of mandarin trees, which allowed to reduce the water stress integral (SΨ; obtained from stem water potential values) by 26.9 and 12.5% under CTL and RDI, respectively, due to the higher water conservation in the soil profile. On the other hand, D2 increased the SΨ of mandarin trees by 54.6 and 40.6% for CTL and RDI, respectively. Therefore, the feasibility of implementing a diversified cropping system on a pre-established MC depends on the spatial and especially temporal distribution of the alley crops.