The use of smartphones has grown significantly in our digital culture. Parallel with the growing use of smartphones, musculoskeletal problems and neck pain associated with intensive smartphone use have also increased. Aim: Evaluate the effect of McKenzie neck exercises on neck pain and disability in smart phone user's adolescents. Design: A quasi experimental research design was utilized. Subjects: A stratified simple random sample of 60 students were recruited.  Setting: The study was conducted at three schools in Tanta city at Gharbeya Governorate. Tools: Three tools were used: Tool I: structured interview schedule. Tool II: Smart phone addiction short version scale. Tool III: The Neck Pain and Disability scale. Results: The majority of the studied adolescents had medical history of neck pain. There was gender differences in smart phone addiction as the majority of the male adolescents were smart phone addicted compared to female adolescents.  There was statistically significant differences   in the mean score of total neck pain and disability in the studied adolescents before and after the application of Mckenzie neck exercises program. Conclusion: Mckenzie neck exercises were effective in decreasing neck pain and related disability in smart phone user's adolescents.  Recommendation: Continues educational programs to adolescents about the importance of neck strengthen exercises and ergonomic posture positions during smart phone uses.