Despite the documented social, economic, and environmental benefits of agroecological innovations, their adoption remains limited, particularly in sub-Saharan Africa. This study focuses on biopesticides as a sustainable alternative for smallholder farmers and examines the often-overlooked behavioral and socio-psychological drivers of adoption. Applying an extended Theory of Planned Behavior (TPB), we surveyed 400 farmers in Huambo Province, Angola, and employed structural equation modelling. Perceived behavioral control (β = 0.312, p = 0.015) and subjective norms (β = 0.301, p < 0.001) were the strongest direct predictors of intention. Additionally, perceived compatibility indirectly influenced intention via subjective norms (β = 0.136, p = 0.035), while perceived resources acted through perceived behavioral control (β = 0.126, p = 0.033). The findings underscore the added value of integrating context-specific constructs, notably perceived compatibility and perceived resources, indicating that when biopesticides are seen as locally accessible and compatible with existing practices, adoption becomes more feasible and socially reinforced. The extended TPB examined herein offers critical insights into policy, training, and sustainable agricultural intervention shaping in resource-constrained, post-conflict settings.