Background Teachers' stress, affect and general occupational well-being influence their teaching and their students. However, how teachers' daily physiological stress and positive affect are related in the classroom is unknown. To reduce teachers' stress and enhance their positive affect, it is crucial to understand how occupational well-being relates to stress and affect.

Aim The aim of the study was to examine the relationships between teachers' daily physiological stress and positive affect in authentic classroom settings and the roles played by teachers' self-efficacy beliefs, perceptions of school climate and burnout symptoms in daily stress and affect.

Sample The sample consisted of 45 classroom teachers.

Method Daily physiological stress was assessed by measuring salivary cortisol levels three times in two days. Positive affect was reported by experience sampling at the same time that cortisol was collected. Questionnaires were used to assess self-efficacy beliefs, perceptions of school climate and burnout symptoms. Three-level modelling with random intercepts and slopes was used to analyse the relationships between daily stress and affect and the effect of teachers' general occupational well-being on stress and affect.

Results No relationships were evident between teachers' physiological stress and positive affect or between daily changes of stress and affect. Self-efficacy beliefs were related to lower stress and higher affect in the middle of the school day. Having sufficient school resources were related to higher positive affect. Teachers' burnout symptoms were associated with lower positive affect.

Conclusions We emphasize the potential for self-efficacy and perceptions of school resources as targets for intervening in teachers' stress and affect.