Alcohol use among people living with HIV (PWH) has been increasingly recognized as an important component of HIV care. Transdiagnostic treatments, such as Acceptance and Commitment Therapy (ACT), that target core processes common to multiple mental health and substance-related problems, may be ideal in HIV treatment settings where psychological and behavioral health comorbidities are high. In advance of a randomized clinical trial (RCT), the overall objective of this study was to systematically adapt an ACT-based intervention originally developed for smoking cessation, into an ACT intervention for PWH who drink at hazardous levels. Consistent with the ADAPT-ITT model, the adaptation progressed systematically in several phases, which included structured team meetings, three focus group discussions with PWH (N = 13), and in-depth interviews with HIV providers (N = 10), and development of standardized operating procedures for interventionist training, supervision, and eventual RCT implementation. The procedures described here offer a template for transparent reporting on early phase behavioral RCTs.