In this study, a 3-D finite element (FE) analysis was used for estimating the lateral capacity of piles driven in sand soils. The effects of different properties of the sand on the p-y curves were studied. Using the results of FE analysis, a model for predicting p-y curves for sandy soils was developed based on the pile shape, which is a combination of tangent hyperbolic and power functions. The results of the developed model were used to demonstrate its applicability in obtaining the p-y curves for the piles driven in sand soils having increase in modulus of elasticity with depth, in sand layers with different modulus of elasticity and unit weight, and at different overburden pressures. The results of the developed model were compared to the results of full-scale pile load test that was conducted at Mustang Island, which demonstrates the ability of the model for predicting the p-y curves and lateral behavior of piles in sandy soils with good accuracy. The results of this study showed that there is little reliability on the results obtained from Reese model, which is the most common method for obtaining lateral behavior of the piles. To consider uncertainties in soil properties due to pile installation, ranges of 0.5 to 1.0 and 1.0 to 2.0 for the value of K in the developed model were proposed for non-displacement and displacement piles, respectively.