Mass media and communication interventions can play a role in increasing HIV testing among gay, bisexual and other men who have sex with men (GBMSM). Despite the key role of social marketing principles and visual design within intervention development of this type, evidence is limited regarding interventions’ social marketing mix or visual design. As part of a systematic review, intervention content was assessed using social marketing theory and social semiotics. Data were extracted on the nature of the intervention, mode of delivery, use of imagery, content and tone and the eight key characteristics of social marketing. Data were synthesised narratively. Across the 19 included studies, reference to social marketing principles was often superficial. Common design features were identified across the interventions, regardless of effectiveness, including: the use of actors inferred to be GBMSM; use of ‘naked’ and sexually explicit imagery; and the use of text framed as statements or instructions. Our results suggest that effective interventions tended to use multiple modes of delivery, indicating high social marketing complexity. However, this is only part of intervention development, and social marketing principles are key to driving the development process. We identified consistent aspects of intervention design, but were unable to determine whether this is based on evidence of effectiveness or a lack of originality in intervention design. An openness to novel ideas in design and delivery is key to ensuring that evidence-informed interventions are effective for target populations.