PURPOSE: The main objective of this study is observing the effects of the functional postural trunk exercise (FPTE) on deep cranio-cervical flexor (CCF) muscle endurance applied on neck pain patients suffering from the acute whiplash-association disorder (WAD). METHODS: The study was tested with 47 patients with neck pain. All patients were equally treated with the ordinary therapy, only experimental group (n=23) was treated with FPTE: assumption of an upright lumbo-pelvic and spinal postural position, adding a neck lengthening manoeuvre in addition. Patients attended physical therapy for 3 times a week, for 4 weeks. Visual analogue scale (VAS) for pain, neck disability index (NDI), range of motion (ROM), were recorded both before and after the intervention. Also muscle activity in the CCF test was employed to analyze the changes between before and after. RESULT: After 4 weeks of training intervention, a remarkable increase in muscle endurance, rotation, extension ROM (p<.05) and decrease in pain and NDI (p<.05) in both groups. Further, the differences between groups were muscle endurance (F=60.350, p<.01), pain, and the left rotation ROM (p<.05). CONCLUSION: From the results, the experimental group had significant the increase in muscle endurance, and the significant decrease in pain. Whilst further research in this category is necessary, these observations suggest that applying exercise in early diagnosis can be of help to treat the neck pain patients suffering from the WAD.