Background: The prevalence of neck pain and neck dysfunction is high in general population. However, there is little literature on the relationship and factors affecting neck pain and neck dysfunction. Objective: To investigate the correlation between neck and shoulder pain, headaches, neck and shoulder dysfunction, and sleep quality in adults with chronic neck pain, and factors affecting neck pain and neck dysfunction. Design: Cross-sectional study Methods : The sample included 114 subjects, who had complained of chronic neck pain for more 12 weeks. We conducted a Pearson's correlation between neck and shoulder pain, headaches, neck and shoulder dysfunction and sleep quality and a regression analysis of the related variables, thereby analyzing factors affecting neck pain and neck dysfunction. Results : In the present study, in adults with chronic neck pain, neck pain was positively correlated with the Neck Disability Index (NDI), Shoulder Pain and Disability Index (SPADI)-Pain score, and SPADI-Total score (p<.05). The NDI was positively correlated with neck pain, SPADI-Pain score, and SPADI-Total score, as well as with Pittsburgh Sleep Qulity Index(PSQI-K) (p<.05). Among the factors affecting neck pain, shoulder disability as assessed by the SPADI was a significantly associated with neck pain, while shoulder pain and shoulder disability determined by the SPADI were identified as significant variables among the factors affecting neck disability. Conclusion : These results indicated that as neck pain worsened, shoulder pain and neck and shoulder dysfunction also increased, which suggested that shoulder disability affected neck pain. In addition, as the neck dysfunction increased, neck pain and shoulder pain and shoulder dysfunction increased, and sleep quality deteriorated, which suggested that shoulder pain and shoulder disability affected neck disability.