This cross-sectional study sought to investigate teachers’ experiences of work intensification and wellbeing. Using the Job Demands-Resources model as a framework, this study investigated the relationship between work intensification, satisfaction with workload, perceived organisational support, and burnout. An Australian sample of 215 high school teachers completed a confidential and anonymous online survey battery. Multiple regression analyses indicated that non-teaching-related workload was a stronger predictor of burnout than teaching-related-workload. In addition, the results indicated that perceived organisational support moderated the relationship between work intensification and the emotional exhaustion component of burnout. These findings have important implications for teacher wellbeing and highlight the importance of organisational support for staff.