Cervical pillow height plays a crucial role in maintaining optimal spinal alignment during sleep, yet standardised measurement protocols and understanding of biomechanical implications remain inconsistent across the literature. This review examines current methodologies for measuring cervical pillow height and analyses the biomechanical consequences of various pillow heights on cervical spine alignment, muscle activity, and sleep quality. A systematic search of major databases revealed significant heterogeneity in measurement techniques, ranging from simple ruler measurements to sophisticated pressure mapping systems and 3D postural analysis. The biomechanical literature demonstrates that inappropriate pillow height can lead to cervical lordosis alteration, increased muscle tension, and compromised sleep quality. However, optimal pillow height appears to be highly individualised, depending on factors such as sleep position, body anthropometry, and existing spinal pathology. Current evidence suggests that personalised pillow height selection based on individual cervical curvature and sleeping posture may be more effective than universal recommendations. Future research should focus on developing standardised measurement protocols and establishing evidence-based guidelines for pillow height selection to optimise cervical spine health during sleep.