Background and aims Persistent neck pain is common and can be detrimental to the health of those who are affected. This is particularly common after neck trauma, where it poses a challenge to health care providers. In this paper, we present the design and results of a study aimed primarily at assessing the feasibility of a supervised exercise intervention for patients with persistent neck pain after trauma. As a secondary aim, we analyzed the results of the intervention. Methods We designed and conducted a feasibility study using a mixed methods design. Ten patients with persistent neck pain (nine with a history of neck trauma and one with sudden onset of neck pain) were recruited from a specialized pain rehabilitation center and underwent a gym-based individual exercise therapy intervention, supervised by a physical therapist. We assessed the feasibility of the exercise therapy intervention based on the experiences of the patients and physical therapists. We analyzed both quantitative and qualitative results using descriptive statistics, content analysis, and questionnaires. Results The study found the exercise therapy to be a feasible alternative for patients with persistent neck pain. Most of the practical aspects of the intervention and study were executed as planned, and the study was well received by the patients, who found it a valuable part of their rehabilitation. In the quantitative analysis, improvements were observed on the Neck Disability Index, numerical rating scale for pain, EuroQol 5D, and physical activity, with scores on the Neck Disability Index showing a statistically significant improvement. Scores on the Disability Rating Index showed a non-significant deterioration. The qualitative analysis uncovered one overarching theme and four themes for the patients and three themes for the physical therapist. Conclusions The exercise therapy intervention seems to be feasible with favorable outcomes for the patients. The quantitative and qualitative analyses demonstrated exercise therapy to be beneficial from several different perspectives. However, although structured, the training needs customization and individual adaption from a clinical reasoning perspective in order to meet each patient's individual needs. Implications This study shows that supervised gym-based exercise therapy is feasible for patients with severe, persistent neck pain. It facilitates and motivates the execution of a larger, controlled trial, which might then lead to a new and potentially effective addition to the toolbox of all health care providers treating patients with persistent neck pain.