A calibration for directional sensitivity of a conical hot film anemometer probe is described. It is usually assumed that the conical probe is insensitive to the velocity vector direction but, in fact, this is not so because deviations of ±60% of the mean velocity can occur at low water speeds. In this study, the probe is aligned at right angles to the velocity vector but the trend of the results applies to probes aligned along the velocity vector. An application of the conical probe to velocity measurements in a vortical water flow for speeds from 0.06 to 3 m/sec is discussed.