Background: Implementation of new effective treatments involves training, supervision and quality control of therapists, who are used to utilize other methods. Not much is known about therapists' views on how new psychotherapy methods should be taught. Objective: The purpose of this study is to get insight in how experienced therapists experience the training in a new method so that training methods for experienced therapists can be improved. Method: Qualitative research using focus groups. For an RCT on the effectiveness of schema therapy (ST) for six personality disorders more than 80 therapists were trained in ST. They applied the ST-protocol after 4-day training, with peer supervision and limited expert supervision. Sixteen of these trained ST therapists from seven health institutions participated in the focus groups. The transcripts and records of the focus groups were analyzed on repeating themes and subthemes and in terms of higher order categories. Results: Therapists appreciated didactical learning methods but particularly valued experiential learning. Especially, novice ST therapists missed role plays, feedback to learn required skills and attitudes, and attention to their resistance to new techniques (e.g., empathic confrontation and imagery). Peer supervision gave emotional recognition, but therapists lacked regular advice from an ST-expert. Conclusions: In teaching a new therapeutic method didactic teaching is necessary, but experiential learning is decisive. Experiential learning includes practicing the new therapy and reflecting on one's experiences, including resistance against new methods. Emphatic confrontation, case conceptualization, role play, peer supervision and opportunities to ask an expert supervisor during peer supervision are found to be helpful.