<b><i>Introduction:</i></b> Not all patients with suboptimal weight loss after bariatric surgery are willing to participate in postoperative behavioral intervention to improve their weight loss. The objective of this study was to explore barriers to and facilitators of participation in postoperative behavioral intervention. <b><i>Methods:</i></b> Thirty semi-structured interviews were conducted with patients (18), physicians (6), and therapists (6) (i.e., psychologists, dieticians, or physiotherapists). A thematic analysis approach was used. <b><i>Results:</i></b> Emotional responses caused by confrontation with suboptimal weight loss hampered patients’ deliberation about participation; insufficient exploration of their need for help limited patients’ ability to make informed decisions; patients were receptive to their physician’s advice when their physician respected their autonomy; using visual weight loss graphs helped to explain suboptimal weight loss to patients; and financial costs and time constraints obstructed participation. <b><i>Conclusions:</i></b> To improve adequate intervention participation, healthcare providers should focus on emotion regulation, support patients in exploring their own need for help, and respect patients’ autonomy.