<p>Chronotype is one’s inherent preferred pattern of sleep and activity within a 24 hour period. Late chronotypes in particular are prevalent among university students and have been associated with differences in physical activity and cognitive performance compared to earlier chronotypes. While these effects have been studied in isolation and in controlled settings, the interaction between chronotype, cognition and physical activity in free-living settings has not yet been studied. The aim of this study was to investigate associations between self-reported chronotype, objective physical activity patterns, and cognitive performance in a naturalistic setting. Seventy-five young adults (age = 25 ± 7 years; 57% female) completed the Composite Morningness Questionnaire to classify chronotype, before wearing accelerometers for seven days. During this time participants completed executive function tasks at the start and end of the day, without modifying their regular sleep-wake hours. Early chronotypes were more physically active compared to late chronotypes, had an earlier time of peak activity, and exhibited shorter reaction times and fewer errors compared to late chronotypes, particularly in the morning. In fully adjusted models, end-of-day testing as well as being active in the hour prior to testing were associated with better cognitive performance. These results suggest that in free living settings, early chronotypes are associated with both better executive function and higher activity levels in the morning, but that activity levels can improve cognitive performance regardless of time of day. Further research could consider whether physical activity could be leveraged to support morning cognitive function in real-world contexts.</p>