Background Discharge from hospital presents significant risks to patient safety, with up to one in five patients experiencing adverse events within 3 weeks of leaving hospital. Aim To describe the frequency and types of patient safety incidents associated with discharge from secondary to primary care, and commonly described contributory factors to identify recommendations for practice. Design and setting A mixed methods analysis of 598 patient safety incident reports in England and Wales related to 'Discharge' from the National Reporting and Learning System. Method Detailed data coding (with 20% double-coding), data summaries generated using descriptive statistical analysis, and thematic analysis of special-case sample of reports. Incident type, contributory factors, type, and level of harm were described, informing recommendations for future practice. Results A total of 598 eligible reports were analysed. The four main themes were: errors in discharge communication (n = 151; 54% causing harm); errors in referrals to community care (n = 136; 73% causing harm); errors in medication (n = 97; 87% causing harm); and lack of provision of care adjuncts such as dressings (n = 62; 94% causing harm). Common contributory factors were staff factors (not following referral protocols); and organisational factors (lack of clear guidelines or inefficient processes). Improvement opportunities include developing and testing electronic discharge methods with agreed minimum information requirements and unified referrals systems to community care providers; and promoting a safety culture with 'safe discharge' checklists, discharge coordinators, and family involvement. Conclusion Significant harm was evident due to deficits in the discharge process. Interventions in this area need to be evaluated and learning shared widely.