Two field experiments have been carried out during two summer season (2022 and 2023) aims for studying the combined effect of a nano-N-P-K fertilizer with as well as without the compost in presence of the mineral N-P-K fertilization on some properties of the cowpea (Vignaunguiculata L. Walp) crop production under saline soil conditions. The experiment was set at Sahl El-Hessiana Agricultural Research Station (El-Sharkia Governorate-Egypt) in a 3-replicates split-plot scheme. It has been found that fertilization by the compost with the prepared nano-N-P-K fertilizer with or without the N-P-K-mineral fertilization improves a number of soil chemical characteristics such as decreasing pH and salinity, and increasing available N, P and K contents in soil. Weight of pods/plant (g), seeds/plant (g), 100-seeds (g), and yield (ton fed-1, (fed=0.42 ha)) of pods and seed were increased by compost and nano-N-P-K fertilizations. It can be concluded from this study that compost and nano-fertilizers in a combination addition with the N-P-K mineral fertilization has improved soil nutrients' status and the estimated yield component and production of cowpea crop in saline soil conditions.