Background: Forward head posture (FHP) of the craniocervical region is one of the most common poor postures. The craniovertebral angle (CVA) is one of the most common methods to evaluate this posture. The LONGUS COLLI (LCo) muscle is an important muscle to control head posture. Objectives: This study aimed to evaluate the relationship between CVA and thickness of LCo in women with FHP. Methods: This case-control research included 35 women with FHP and a control group. Sagittal view photography of the cervical spine was used for measurement of CVA. An ultrasonography device measured the thickness of the LCo. Correlation between CVA and thickness of LCo was determined using correlation coefficient in both groups. Results: Our findings showed a non-significant correlation between the CVA and thickness of LCo in case and control groups. Conclusions: According to the results of this study, there was no significant correlation between a lower CVA and smaller thickness of LCo.