Active motion examination of patients with cervical spine-related pathologies is necessary to establish baseline function, set physical therapy goals, and choose interventions. This study investigated the sagittal plane active range of motion (ROM) of the global (GCS) and upper cervical spine (UCS) in relation to age and sex in healthy volunteers. One hundred twenty-two volunteers aged 18 to 75 years participated. Volunteers were excluded if they displayed any characteristic that could affect cervical spine ROM. GCS and UCS flexion and extension were each measured three times using a CROM device. Linear regression models (LRMs) were developed to explore the relationships between age and sex and GCS and UCS ROM. The LRM for age showed a decrease in GCS flexion (-2.01°), GCS extension (-3.33°), and UCS extension (-1.87°) for every decade of increasing age. The LRM for sex showed that men displayed less ROM than women in GCS extension (-6.52°) and UCS extension (-2.43°). These results suggest an age-related loss of sagittal plane GCS ROM and UCS extension ROM, and sex-related differences in GCS and UCS extension with women having greater motion than men.