Introduction Soft-tissue mallet finger occurs due to loss of terminal extensor tendon secondary to rupture of distal phalanx. Although using noninvasive splints for 6-8 weeks is the gold standard for conservative treatment of closed soft-tissue mallet injuries, patient compliance is an important factor impacting on patient outcomes. In this study, we used a single Kirschner Wire (K-W) to fix the distal interphalangeal (DIP) joint in extension in those patients failed to comply with routine splinting. Materials and methods In this prospective study, 190 patients with Doyle type 1 closed soft-tissue mallet finger deformity were included in four groups between 2011 and 2015. These groups were determined according to treatment modalities. Patients in the first group were treated with a finger splint (n = 109). Patients in the second group first received a finger splint and then K-W was applied due to lack of adequate compliance (n = 23). Patients in the third group were treated with K-W only (n = 47), and the fourth group did not accept surgical treatment nor conservative treatment (n = 11). After 20 weeks of follow up, we evaluated the results with functional measurements according to Crawford criteria and patient satisfaction. Additionally, the mid-term outcome was assessed with a follow-up at 2 years. Results At 20th week postoperatively, average DIP extension lag was 6 degrees (0-30) for the first group, 6.1 degrees (0-30) for the second group, 3.8 degrees (0-25) for the third group, and 17.3 degrees (7-30) for the fourth group. Total patient satisfaction was 85%, which was considered excellent or good. Swan neck deformity was observed in 11% of patients. Osteomyelitis and KW related complications were not observed. There were no statistically significant differences between short-term and mid-term results. Conclusion Internal fixation via K-W may be a suitable treatment option compared to splint therapy for management of closed soft-tissue mallet finger in noncompliant patients. Using this treatment approach, the success rate for patients could satisfactorily be improved.