Baroreceptor cardiac reflex sensitivity is reduced in hypertension and is considered a powerful prognostic factor in cardiovascular health. This study analyzes the acute effects of a brief respiratory training on baroreceptor sensitivity and on two new proposed baroreflex parameters: baroreceptor power (i.e., the percentage of cardiac beats regulated by the baroreflex) and effectiveness (i.e., the frequency in which the baroreflex responds to transient alterations in blood pressure). Twenty-two participants, 10 primary mild hypertensives and 12 normotensives, learned and practiced a respiratory pattern characterized by breathing at 6 bpm, with time of expiration being twice time of inspiration, predominantly abdominal, and with pursed lips. Baroreceptor parameters are differentiated in terms of increases ("up" sequences) or decreases ("down" sequences) in blood pressure. Irrespective of the groups, the breathing manipulation increased baroreceptor sensitivity (only in the "up" sequences), power, and effectiveness (only in the "down" sequences). These results suggest that this type of respiratory training could be used as a promising intervention to increase baroreceptor cardiac function in primary hypertension.