A method to measure the melt temperature distribution in an injection mold cavity is developed. A thermocouple is used in the construction of a sensor with a tip that can be adjusted at different depths of a mold cavity, to measure temperature profiles at different positions in the mold. Polymer temperature distributions are measured and factors affecting temperatures and the key variables that influence distributions are determined. Measurements are compared with temperatures obtained from numerical simulation of the injection molding process using a three-dimensional heat transfer analysis. Although showing lower values and generally higher cooling rates, temperature data measured from the mold cavity indicate similar behavior to predicted transient temperature distributions.