Implementation intentions specifying the replacement of a habitual response with an alternative response in a critical situation can overrule habits. In three experiments the cognitive effects of such counterhabitual implementation intentions were investigated. Results showed that implementation intentions eliminated the cognitive advantage of the habitual means in the “horse race” with the alternative response. That is, in the control condition, the habitual means was more accessible than the alternative means on encountering the critical situation, but this was no longer the case when implementation intentions were formulated. However, the cognitive advantage of the habitual means was not immediately replaced by an automatic activation of the alternative means. This suggests that formulating counterhabitual implementation intentions increases individuals’ flexibility to choose which behavior to perform in the critical situation but that actual behavior will depart from their habits only to the extent that individuals have strong alternative goal intentions.