Background: A mallet finger (MF) is diagnosed clinically and can be managed in primary care. The actual incidence of MF and how it is managed in primary care is unknown. Aim: To determine the incidence of MF in primary care and to obtain estimates for the proportions of osseous and tendon MF. An additional aim was to gain insight into the management of patients diagnosed with MF in primary care. Design & setting: A cohort study using a healthcare registration database from general practice in the Netherlands. Method: Patients aged ≥18 years with a new diagnosis of MF from 1 January 2015–31 December 2019 were selected using a search algorithm based on International Classification of Primary Care (ICPC) coding. Results: In total, 161 cases of MF were identified. The mean incidence was 0.58 per 1000 person–years. A radiograph was taken in 58% (n = 93) of cases; 23% (n = 37) of cases had an osseous MF. The most applied strategies were referral to secondary care (45%) or conservative treatment in GP practice (43%). Overall, 7% were referred to a paramedical professional. Conclusion: On average, a Dutch GP assesses ≥1 patient with MF per year. Since only a minimal number of patients required surgical treatment and a limited number of GPs requested radiography, the recommendation in the guidelines to perform radiography in all patients with MF should potentially be reconsidered. The purpose of requesting radiographs should not be to distinguish between a tendinogenic or osseous MF, but to assess whether there is a possible indication for surgery.