The propagation characteristics of high‐frequency echolocation signals (peak energies above 100 kHz) of the beluga (Delphinapterusleucas) were measured while the animal performed a target detection task. The whale was trained to station on a bite plate so that its transmission beam could be measured in the vertical and horizontal planes using hydrophone arrays. The transitional region between the acoustic near‐ and farfields was also located using an array of hydrophones that extended directly in front of the animal in the horizontal plane. Three distinct modes of signals were observed. Mode 1 signals had click intervals greater than the time required for the signals to travel to the target and back (two‐way transit time). Mode 2 signals had click intervals shorter than the two‐way transit time, and mode 3 signals had high repetition rates with an average click interval of 1.7 ms, approximately 2% of the two‐way transit time. The average click intervals for the modes 1 and 2 signals were 193 and 44 ms, respectively. The vertical and horizontal beam patterns of the mode 1 signals had similar 3‐dB beamwidths of approximately 6.5°. The major axis of the vertical beam was directed approximately 5° above the plane defined by the animal’s teeth. The near‐ to farfield transition region was approximately 0.64–0.75 m from the tip of the animal’s mouth.