Implementation intentions are plans that specify the when, where, and how of goal striving in advance, and have been shown to enhance rates of goal attainment compared to merely forming respective goal intentions. The present research investigated whether the accessibility of the specified situation (cue accessibility) and the strength of the association between the specified situation and the intended response (cue-response linkage) explain the impact of implementation intentions on goal achievement. Findings indicated that participants who planned to undertake a verbal task better attained their goal compared to participants who did not form a plan. Crucially, implementation intention effects were mediated by the accessibility of the specified cue and by the strength of cue-response links. These findings support the idea that implementation intentions benefit performance because control of behavior is delegated to specified situational cues that initiate action automatically.