Intercropped systems are often more productive per unit area (LER>1) and unit of water uptake (WER>1) than sole systems. Using the Yield-SAFE and Farm-SAFE simulation models, the possibilities of intercropping in walnut orchards in the future climatic conditions of our region were analyzed from the aspect of productivity and profitability. Furthermore, the productivity and water use efficiency in walnutbuckwheat, walnut-barley and walnut-maize systems were assessed, and during the maize growing season, the microclimate and growth, yield components and the use of water and nutrients of maize were analyzed in detail. The models estimated that, despite the reduction in crop yields, intercropped systems would be more productive than monoculture systems, even after 20 years. The simulated scenario with intercropping for six years and then maintaining a sole orchard proved to be the most profitable during the simulated period of 20 years. A significant impact on the microclimate was recorded in the older orchard, which is the result of larger walnut trees and narrower planting distances. LER values were 1.05, 1.32, and 1.53, and WER 1.12, 1.31, and 1.83 for buckwheat, maize, and barley systems, respectively. In the walnut-maize system, a negative effect of walnut trees on the germination of maize was observed, which resulted in a significantly lower yield per total area compared to the yield of monoculture maize. However, intercropped maize achieved a higher harvest index and significantly higher 1000 kernel weight. No significant differences were found between observed maize systems in productivity per unit of available nutrients in the soil, nor in the efficiency of mobilization of available nutrients into grain. Nevertheless, intercropped maize produced a higher grain yield per unit of absorbed nitrogen and potassium. This research showed that intercropping arable crops in walnut orchard can be a sustainable measure of agricultural production intensification or a cost-effective way of switching from arable to fruit production.