In the design of full-scale piles in the field, base geometry effects are usually not considered on the base resistance calculations due mainly to the limited research and lack of reliable data. In this paper, the effect of two base geometries (flat and conical) on the base resistance of model piles in sand is studied by performing a series of tests in a half-cylindrical calibration chamber with image analysis capabilities. Detailed displacement and strain fields obtained with the Digital Image Correlation (DIC) technique and base resistance measurements obtained with miniature load cells installed in the base of model piles demonstrate that the addition of a conical base to a pile significantly change the deformation pattern of the sand around the base during loading and the magnitude of the unit base resistance. The DIC analyses revealed that soil elements located at corresponding positions in the sand domain undergo up to 30% more displacement below the model pile with a flat base than when the model pile has a conical base. Moreover, the magnitude of the volumetric strains at the soil-pile interface is between 30% and 40% greater at the corner of the flat-base than next to the shoulder of the conical-base model pile. The ratio of the unit base resistance qb of a pile with a conical base to the qb of a model pile with a flat base ranges from 0.75 to 0.84 at relative displacement levels equal to 10% of the diameter B of the model pile and from 0.70 to 0.84 at greater relative displacements. The results of this research also indicate that the ratio of the ultimate unit base resistance to cone resistance (qb,10%/qc) depends significantly on the base geometry and ranges from 0.95 (in medium-dense sand) to 1.27 (in dense sand) for displacement piles, and from 0.09 (in medium-dense sand) to 0.15 (in dense sand) for nondisplacement piles.