: A boundary conduction mode (BCM) control can reduce both turn-on and turn-off losses by turning switches on at zero current point and lowering the peak values of the phase currents compared to discontinuous conduction mode (DCM) control. However, when applying the BCM control in a two-parallel interleaved Vienna rectifier, the interleaving operation generates circulating current, which alters the slopes of the phase currents. This prevents the single-Vienna BCM control from deriving the proper switching frequency for BCM operation, which leads to phase current distortion and failure in loss optimization. This paper proposes an optimized BCM control for a two-parallel interleaved Vienna rectifier. The proposed BCM control determines the switching frequency by predicting the slope of the phase currents for each converter, taking into account the effect of circulating current. Consequently, the accurate BCM operation is achieved, thereby reducing power losses and input current distortion. The effectiveness of the proposed control is verified through simulation results.