Objectives <p>To investigate the relationship between ossification of nuchal ligament (ONL) with both craniocervical posture and craniofacial morphology.</p> Methods <p>This cross-sectional study involved 256 participants with and without ONL. The craniocervical and craniofacial characteristics of each participant were assessed through a software analysis of their cephalograms, containing 37 variables. Sex-based and age-based stratified analyses were also performed. The intergroup differences were examined by the independent sample t-test and the Mann-Whitney U test. Two-way ANOVA was used to assess the effects of gender and ONL status on craniocervical posture and facial morphology.</p> Results <p>In overall analysis, the ONL group showed greater C0-C1 and craniocervical angle than the normal group. Several craniofacial variables (SNA, ANB, MP-NPog, angle of convexity, convexity of point A, and U1-NA) also differed significantly. In age-stratified analysis, adult patients showed results consistent with the overall trend. For stratified analysis based on sex, the differences of male subjects in C0-C1, craniocervical angle, SNA, and MP-NPog between the two groups were statistically significant. For female subjects, the differences in C0-C1, craniocervical angle, ANB, and U1-NA between the two groups were statistically significant. Two-way ANOVA revealed no significant interaction effect between gender and ONL status.</p> Conclusions <p>ONL is associated with pronounced forward head posture and distinct craniofacial feature. These morphological alterations may serve as diagnostic indicators for ONL.</p> Graphical Abstract <p></p>