We present five experiments that examined Wegner’s (1994) theory of ironic processes of mental control in reactive motor performance under pressure for the first time. In Experiments 1, 2 and 4, we conducted specific examinations of the incidence of ironic error using a reactive motor task. In Experiments 3 and 5 we provided the first tests of whether task instruction moderates the incidence of ironic errors. The task required participants to react to a series of three primary color balls as they rolled down a chute under low- and high-anxiety conditions. Measures of anxiety, heart rate, heart rate variability and muscle activity confirmed the effectiveness of the anxiety manipulation. Experiments 1, 2 and 4 revealed that anxiety increased the number of ironic errors. In Experiments 3 and 5, we provided the first evidence that instructional interventions can reduce the incidence of anxiety-induced ironic performance errors in reactive motor tasks.