Sugarcane is vital to Belize’s economy, significantly contributing to its Gross Domestic Product and supporting a large portion of the population. It is necessary to address the declining soil health in this nation due to excessive chemical fertilizer use, and Belize aims to promote organic fertilizers, which enhance soil quality and reduce environmental impacts. The primary purpose of this study was to investigate the determinants of adoption intentions regarding organic fertilizers among Belizean sugarcane farmers using the Extended Theory of Reasoned Action. Data were collected from 207 farmers in the Orange Walk and Corozal districts using a non-probability sampling approach via a self-administered questionnaire measuring perceived health risks, environmental concerns, attitudes, subjective norms, and adoption intentions. The results revealed that both perceived health risks and environmental concerns influenced farmers’ attitudes and subjective norms, which, in turn, affected their adoption intentions, as revealed through path analysis; socio-economic factors, years of farming experience, and ownership background partially affected adoption intentions regarding organic fertilizers, as determined via binary logistic regression analysis. The findings suggest that raising farmers’ awareness of health risks and environmental crises, as well as enhancing farmers’ knowledge and their positive attitudes towards the use of organic fertilizers, will contribute to the sustainable development of the sugarcane industry in Belize. Some interventions by policymakers are recommended to support the transition to the use of organic fertilizers in sugarcane farming.