Objective To gain insight into factors involved in attrition from hospital-based medical specialty training and future career plans of trainees who prematurely left their specialty training programme. Design Nationwide online survey study. Setting Postgraduate education of all hospital-based specialties in the Netherlands. Participants 174 trainees who prematurely left hospital-based medical specialty training between January 2014 and September 2017. Main outcome measures Factors involved in trainees’ decisions to leave specialty training and their subsequent career plans. Results The response rate was 38%. Of the responders, 25% left their programme in the first training year, 50% in year 2–3 and 25% in year 4–6. The most frequently reported factors involved in attrition were: work-life balance, job content, workload and specialty culture. Of the leaving trainees, 66% switched to another specialty training programme, of whom two-thirds chose a non-hospital-based training programme. Twelve per cent continued their career in a non-clinical role and the remainder had no specific plans yet. Conclusions This study provides insight in factors involved in attrition and in future career paths. Based on our findings, possible interventions to reduce attrition are: (1) enable candidates to develop a realistic view on job characteristics and demands, prior to application; (2) provide individual guidance during specialty training, with emphasis on work-life balance and fit with specialty.