<p>Action selection is traditionally thought to be governed by dual top-down control systems: a fast, affect-dependent controller and a slow, experience-driven controller. Emerging evidence indicates that bottom-up cardiac phase signals also contribute to action selection by facilitating (i.e., go) or suppressing (i.e., nogo) motor responses. Despite growing interest in cardiac-brain interactions, no prior study has examined whether cardiac phase effects on feedback-driven action decisions are modulated by appetitive and aversive motivational states. We conducted a secondary analysis of a go/nogo functional magnetic resonance imaging (fMRI) dataset (<i>n</i> = 29), retrospectively determining the onset of decision cues relative to physiologically defined cardiac phases. We tested competing behavioural and computational hypotheses proposing that cardiac phase modulated action selection via motivational action biases, or through a general, affect-independent prepotent urge to act. Additionally, we performed an exploratory fMRI analysis to investigate neural activity underlying action decisions as a function of cardiac phase. Converging behavioural and computational evidence showed that systole was associated with a higher likelihood of go responding, independent of motivational action biases. Preliminary fMRI results further suggested that systolic facilitation of action was accompanied by diminished neural activity supporting action inhibition. Together, these findings extend existing evidence that cardiac phase impacts action decisions.</p>