Introduction: Food sharing is increasingly recognized as a strategy to reduce waste and promote sustainability. Online peer-to-peer (P2P) platforms, such as Facebook groups, have emerged as popular channels for redistributing surplus food. However, the dynamics between these anonymous online systems and established local networks remain underexplored, particularly among environmentally conscious individuals. Purpose: This study aims to understand how environmentalists perceive and navigate food sharing, focusing on their motivations, methods, and concerns when choosing between online P2P platforms and local, personal networks. Method: In-depth qualitative interviews were conducted with five environmentalists (two males, three females) in Hong Kong. Participants were asked about their experiences, attitudes, and decision-making processes regarding food surplus management and sharing practices. Results: Participants demonstrated a strong moral commitment to preventing food waste, actively seeking avenues to redistribute surplus items. They identified several advantages of online P2P platforms, including broad reach, convenience, and the ability to quickly match surplus food with recipients outside their immediate social circles. These platforms were especially valued for efficiently diverting packaged or unopened food from landfill. However, considerable concerns were raised about food safety, accountability, and trust when sharing prepared or partially consumed foods with strangers online. Most participants preferred sharing such items within their immediate social circles or local networks, citing higher levels of trust, easier communication, and logistical convenience. Conclusions: Environmentalists approach food sharing as a pragmatic and ethical exercise, leveraging the strengths of online P2P platforms for low-risk, packaged goods while relying on trusted local networks for high-risk, prepared foods. Their practices reflect a balance between maximizing environmental benefits and minimizing health and liability risks, suggesting that effective food surplus management requires both technological solutions and strong community ties.