OBJECTIVES: People with later chronotypes are at greater T2D risk, yet it is unknown if β-cell function differs among chronotypes. Thus we, assessed β-cell function in morning (MORN) and intermediate (INT) chronotypes with obesity. METHODS: Adults ( RESULTS: Age, body composition and VO CONCLUSIONS: β-cell function was higher in MORN versus INT chronotypes. Further work is warranted to discern how chronotype impacts insulin secretion. TRIAL REGISTRATION: NCT03355469.