In this paper, the slope effects on p-y curves in c-ϕ soils have been investigated. Vertical mono-pile under static lateral loading in level and sloped grounds with both cohesion and friction properties has been analyzed. Several concrete and steel pipe piles near soil slopes and level ground have been modeled. The basis of the numerical analysis is 3-D explicit finite difference method. The effects of pile-soil interface properties such as cohesion ratio and friction ratio on the soil response and pile deflections have also been investigated. The results of this research show that the general shape of p-y curves for c-ϕ soils and non-cohesive, granular soils are hyperbolic similar to p-y curves for clayey cohesive soils. This study that presents a new method and new design curves similar to concepts have been proposed by Evans and Duncan for derivation of ultimate soil strength, pu, for piles in c-ϕ soils. There are a few numerical and experimental studies about piles under lateral loading in c-ϕ soils, and present study focuses on this shortcoming.