INTRODUCTION: Social networks play a vital role in influencing individual and collective health behaviors and facilitating the diffusion of health interventions. Fishing communities in sub-Saharan Africa face socio-cultural and occupational challenges such as low literacy rates and high mobility. However, their high social cohesion creates a unique social environment for spreading health interventions. We explored the role of social relationships in mediating health intervention adoption in these communities, to inform future intervention strategies. METHODS: We conducted an exploratory phenomenological qualitative study between September and October 2024 nested within a large community cluster randomized trial (the FISH trial) in fishing communities in Mangochi district on the southern tip of Lake Malawi. We conducted four focus group discussions (N = 47) and 16 in-depth interviews. Data were analyzed thematically using a hybrid deductive and inductive data coding approach. RESULTS: Fishermen's social networks included fishing friendships, kin and broader community connections that facilitated knowledge exchange, resource sharing and support provision. Familiarity, trust, desire to conform to community norms and shared community ties enabled health knowledge exchange and encouraged uptake of targeted interventions for HIV and schistosomiasis, despite fishermen's mobility. Other facilitators at individual level included perceived susceptibility and financial incentives. Occasionally, negative rumors spread through peer networks, e.g., a link between blood sample collection and malign government agenda, contributed to disengagement with health interventions. Other factors including HIV-related stigma and prohibitive traditional beliefs interacted with social networks to hinder uptake. DISCUSSION: Fishermen's health decisions are deeply embedded within their social structures. However, other factors operating at the individual and community level were noted to be crucial catalysts of the decision-making process. This study highlights the potential of leveraging social networks in public health strategies for mobile communities so long as they account for critical individual factors that influence health service engagement.