Across many Pacific Island Countries, food insecurity and malnutrition are on the rise. In response, governments, development agencies, and non-governmental organisations are promoting small-scale aquaculture as a complement to fish supplied through coastal fisheries. While small-scale aquaculture has been widely adopted in parts of Asia and Africa, its adoption in rural Pacific Island communities remains relatively low. In this paper, we draw on Diffusion of Innovation theory and apply a classification tree analysis to model the influence of farmers’ socio-economic attributes, communication channels, and attributes of the innovation, on the adoption of tilapia aquaculture. We compare 40 tilapia aquaculture adopters with 40 non-adopters in rural Solomon Islands. Our results show that farmers’ socio-economic attributes have the highest influence on tilapia aquaculture adoption. Tilapia aquaculture adopters were older, male, less subsistence-oriented, and had lower material styles of life than non-adopters. Information regarding tilapia aquaculture was most shared through informal channels, including relatives and word-of-mouth, compared with formal sources (e.g. fisheries extension officers, expert farmers, pamphlets, and posters). Lastly, while tilapia aquaculture was seen as compatible with socio-cultural norms and livelihood demands, its relative advantage and observability in comparison with other livelihood activities were perceived as low. Overall, this study suggests that tilapia aquaculture (and associated benefits) is not reaching the poorest and vulnerable groups (e.g. women or subsistence-oriented households) in rural Solomon Islands. These findings point to a need for in-depth understanding of socio-economic attributes of farmers, thus ensures strategies to support marginalised groups to participate in and benefit from tilapia aquaculture. The study also highlights the need to better utilise informal and locally appropriate communication channels to effectively support the spread of tilapia aquaculture in rural Pacific Islands contexts. Ultimately, this research can inform small-scale aquaculture development policies of the Government of Solomon Islands, and other Pacific Island Countries, to support the sector in contributing to rural food and nutritional security.