Background: Abnormal head and neck postures play a significant role in developing cervical spine dysfunction. Forward head posture (FHP) is one of the most common findings in individuals who experience head and neck disorders. Objectives: This study used a photographic method to analyze the head, upper neck, and lower neck postures in forward head posture in both static and quasi-static states. Since timely diagnosis and appropriate treatment are important in preventing further complications of this kinematic chain disorder, the postural variables of the head and neck were evaluated by focusing on their separate parts in both static and quasi-static states. Methods: This observational-analytical case-control study included 175 individuals with no history of neck pain in the past 6 months, 138 with FHP, and 37 with non-FHP. The postural angles, including the upper cervical, lower cervical, craniovertebral, head posture, and head tilt angles, were measured through photography in both the static state (with the head and neck in a neutral position) and the quasi-static state (while moving the head and neck in the sagittal plane) in a sitting position. The measurements were taken in two groups (FHP and non-FHP). Results: In a static state, the upper cervical angle was higher in the FHP group than in the non-FHP group. The lower cervical measurements were higher in the non-FHP group than in the FHP group. In the quasi-static state, significant differences existed in the changes of the upper cervical, lower cervical, craniovertebral, head postural, and head tilt angles between the two groups (P-value < 0.05). Conclusions: During full flexion to full extension of the neck, subjects with FHP exhibited reduced mobility in the cervical spine, particularly in the lower cervical region. Additionally, the position of the head relative to the neck remained unchanged in this group.