A threshold detection and capture verification system for a cardiac pacemaker/cardioverter/defibrillator (PCD) of the type comprising an implantable pulse generator (IPG) and a lead system including one or more pacing leads each having a proximal end coupled to the IPG and a distal end with at least one pace/sense electrode in contact with a patient's heart and one or more defibrillation leads having a proximal end coupled to the IPG and a distal end having one or more defibrillation electrodes in contact with a patient's heart or otherwise implanted within the patient's body. In a threshold detection operation, a sense amplifier is coupled to a selected threshold sensing electrode pair comprising at least one and preferably two defibrillation electrodes, and pacing pulses are applied to a pair of pace/sense electrodes. The evoked responses to pacing pulses having energy levels exceeding the stimulation threshold of the heart are detected through the sense amplifier and capture verified. The stimulation threshold is determined by incrementally reducing the pacing pulse energy until an evoked response is not sensed. The pacing pulse energy may then be adjusted to a level providing a safety margin above the stimulation threshold.