ObjectivesThis study set out to understand how (which elements), in what context and why (which mechanisms) interventions are successful in reducing (problematic) alcohol use among older adults, from the perspective of professionals providing these interventions.DesignGuided by a realist evaluation approach, an existing initial programme theory (IPT) on working elements in alcohol interventions was evaluated by conducting semistructured interviews with professionals.Setting and participantsThese professionals (N=20) provide interventions across several contexts: with or without practitioner involvement; in-person or not and in an individual or group setting. Data were coded and links between contexts, elements, mechanisms and outcomes were sought for to confirm, refute or refine the IPT.ResultsFrom the perspective of professionals, there are several general working elements in interventions for older adults: (1) pointing out risks and consequences of drinking behaviour; (2) paying attention to abstinence; (3) promoting contact with peers; (4) providing personalised content and (5) providing support. We also found context-specific working elements: (1) providing personalised conversations and motivational interviewing with practitioners; (2) ensuring safety, trust and a sense of connection and a location nearby home or a location that people are familiar with in person and (3) sharing experiences and tips in group interventions. Furthermore, the mechanisms awareness and accessible and low threshold participation were important contributors to positive intervention outcomes.ConclusionIn addition to the IPT, our findings emphasise the need for social contact and support, personalised content, and strong relationships (both between client and practitioner, and client and peers) in interventions for older adults.