An optical proximity sensor and corresponding methods of measuring crosstalk in the sensor are disclosed. The amount of crosstalk generated between the light emitter and the light detector of an optical proximity sensor is measured and quantified according to one of two methods. The measured crosstalk may then be stored in a register or memory location and then subtracted from signals representative of signals indicative of the nearby presence of an object to be detected combined with crosstalk, thereby removing so the contribution or effect of crosstalk on such signals.