The present study evaluated an implementation intention intervention that aimed to increase attendance at scheduled, initial appointments for psychotherapy by helping clients to manage negative feelings about attendance. Participants received a postal questionnaire that measured their views about attending psychotherapy. One half of the sample was randomly assigned to an implementation intention induction that was embedded in the questionnaire. Intention-to-treat analysis (N=390) indicated that participants who formed implementation intentions were more likely to attend compared to controls (75% vs. 63%), and this effect was even stronger among participants who returned the questionnaire (83% vs. 57%). Whereas anticipated affective costs (e.g., shame) had a negative impact on attendance for most participants, this effect was attenuated when participants formed implementation intentions and perceived that attendance would be beneficial. Thus, implementation intention formation can help clients to deal effectively with negative feelings that might otherwise prevent them attending their first psychotherapy appointment.