Purposes Being diagnosed with oral cancer is a life-threatening life event. It often induces social, emotional and psychological consequences and may cause depressive disorders. The primary aim of this study was to identify and quantify the personal and clinical characteristics involved in depression for patients who have been treated for oral cavity malignancies, with a 5-year follow-up period after treatment. The secondary aim of this study was to identify the clinical factors that increase a patient’s risk of experiencing depression 5 years after treatment. Methods Patients with primary oral cancer were assessed for up to 5 years after primary treatment. A mixed-model analysis was performed, with depression measured by the Center for Epidemiologic Studies Depression Scale as outcome measure. Results A total of 141 patients were included in the study. Factors associated with depression were gender, tumour location and having an emotion-oriented coping style. The occurrence of depression within 5 years after treatment could be reliably predicted by a patient’s gender, the location of their tumour and the extent to which they had an emotion-oriented coping style. Conclusions This study revealed that being female, having a maxillary tumour and having an emotion-oriented coping style are associated with higher levels of depressive symptoms in patients treated for oral cancer up to 5 years post-treatment. A substantial proportion of the patients with oral cancer experienced high levels of depression both before and after their treatment, suggesting that adequate diagnostics and care are needed to try to prevent severe depression in these patients.