Utilizing the job demand-resource theoretical framework, this study expands on previous research by examining the role of teacher workloads in the relationship between teachers’ resources and teacher well-being. The study used data from Taiwanese lower secondary school teachers in the TALIS 2018 survey and conducted a structural equation modeling analysis. The results showed that teacher training preparedness had a direct positive effect on well-being and an indirect effect that was mediated by teaching and student behavior workloads. On the other hand, teachers’ perceived autonomy did not have a direct impact on well-being but was indirectly related to well-being through the teaching workload. Additionally, the study found that teaching and student behavior workloads were negatively associated with well-being. By incorporating workload as a mediator, this study offers new insights into the complex relationship between job demands, resources, and well-being in the teaching profession.