This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Background: Factors within the school environment may impact young people’s mental health and wellbeing. The aim of this study was to understand the association between teacher and student mental health and wellbeing. Further, it seeks to identify possible explanations by examining whether the strength of any association is weakened once quality of teacher-student relationships, teacher presenteeism and absence are considered. Methods: Cross-sectional data were collected from 3217 Year 8 (aged 12-13 years) students and from 1167 teachers in 25 secondary schools in England and Wales. The association between teacher wellbeing (measured by Warwick Edinburgh Mental Wellbeing Scale (WEMWBS)) with student wellbeing (WEMWBS) and with student psychological distress (Total Difficulties Score (TDS)) was assessed using Random Effects Mixed Models. Analyses were repeated using teacher depression (measured by Patient Health Questionnaire) as the explanatory variable. Results: Better teacher wellbeing was associated with i) better student wellbeing (standardised effect =0·07, 95% CI = 0·02 to 0·12) and ii) lower student psychological distress (standardised effect = -0·10, 95% CI = -0·16 to -0·04). Teacher presenteeism and the quality of the teacher-student relationship appeared to be on the pathway of these relationships. Higher levels of teacher depressive symptoms were associated with poorer student wellbeing and psychological distress (standardised effect =-0·06, 95% CI = -0·11 to -0·01 & 0·09, 95% CI = 0·03 to 0·15). This association did not withstand adjustment of teacher presenteeism. Limitations: Cross sectional in design so unable to establish temporal associations. Conclusions: Associations were found between teacher wellbeing and student wellbeing and psychological distress. There were also an association between teacher depression and student wellbeing. Both may be partially explained by teacher presenteeism and quality of teacher-student relationships.This project was funded by the National Institute for Health Research Public Health Research (NIHR PHR) Programme.