Few studies have focussed on the link between anxiety and inhibitory control in the absence of stimulus-driven external threat. This two-part experiment examined the interactions between (1) somatic trait anxiety, somatic situational stress (i.e. threat of electric shock), and effort, and (2) cognitive trait anxiety, cognitive situational stress (i.e. ego-threat instructions), and effort, on inhibitory processes using a Go-No-Go paradigm. Trait anxiety was operationalised using questionnaire scores and effort was operationalised using a visual analogue scale. Performance effectiveness was measured using the d′ parameter from signal detection theory and processing efficiency was indexed by the ratio of d′ to response time on correct trials. Results indicated that somatic trait anxiety and stress did not predict effectiveness or efficiency. Cognitive trait anxiety and stress were associated with both inhibitory effectiveness and efficiency deficits; however, contrary to expectations these deficits were evident at higher rather than lower mental effort. Results suggest a distinction between how somatic and cognitive anxiety manifest on tasks involving inhibitory control.