OBJECTIVES: This study evaluated the immediate effects and acceptability of a smartphone application named NeckProtector to promote neck pain self-management through stretching incorporating deep slow breathing, among smartphone users with neck pain. METHODS: One-hundred participants were recruited in the study. Participants were divided into two groups by block randomized allocation. The researchers gave the NeckProtector application to all participants for acceptability testing by navigation of the application for 20–30 minutes. Next, the treatment group (n = 50) conducted the exercise program via smartphone application for 15–20 minutes, while the control group (n = 50) rested for 20 minutes. Evaluations were performed at baseline and after intervention for pain intensity, muscle tension, pressure pain threshold (PPT), and cervical range of motion (CROM). Quantitative and qualitative feedback was then obtained by an acceptability survey and open-ended questionnaires. RESULTS: The immediate effects showed statistically significant improvements in pain intensity, muscle tension, PPT, and CROM in the treatment group in comparison to the control group. Participants reported a high level of acceptability through ratings on a Likert scale. The qualitative questionnaires received positive responses that the application was easy to use and the exercise program was useful to cope with neck pain. CONCLUSIONS NeckProtector can be an alternative treatment for neck pain self-management via smartphone application among smartphone users with neck pain. Further studies should examine the long-term effectiveness (Clinical trials registry: TCTR20160523001).