Naturally occurring, weakly cemented sand is common along the southern California coast, as is the practice of using cast-in-drilled-hole (CIDH) piles in this type of soil. However, information on the lateral load behavior of piles for this soil type is limited. In current design practice, the standard p-y curves for sand are frequently used to analyze the lateral pile responses in cemented sand by neglecting the resistance from the soil cohesion. However, the accuracy of using these p-y curves for weakly cemented sand has not been evaluated, particularly for a wide range of pile diameters. Therefore, instrumented CIDH piles with diameters ranging from 0.4 to 1.2 m were installed in dense, weakly cemented sand and tested under lateral loading. On the basis of a comparison of backcalculated p-y curves for different pile diameters, the effect of pile diameter on the p-y curves was insignificant at load levels below the ultimate lateral soil capacity. Furthermore, the standard p-y curves currently available in the literature were implemented to compute the pile responses and were compared with the measurements. Using the standard p-y curves underestimated the soil resistance in weakly cemented sand for small diameter piles but tended to overestimate the soil resistance to large diameter piles. Therefore, the use of these standard p-y curves for large-diameter piles in weakly cemented sand should be used with caution.