Both sensory hypersensitivity and hypoaesthesia are features of chronic whiplash associated disorders (WAD). Sensory hypersensitivity is not a consistent feature of chronic idiopathic (non-traumatic) neck pain but the presence of hypoaesthesia has not been investigated. This study compared the somatosensory phenotype of whiplash and idiopathic neck pain. Comprehensive Quantitative Sensory Testing (QST) including both detection and pain thresholds as well as psychological distress were measured in 50 participants with chronic WAD, 28 participants with chronic idiopathic neck pain and 31 healthy controls. The whiplash group demonstrated lowered pressure pain thresholds (PPTs) at all sites compared to the controls (p < 0.01) but there was no difference between the two neck pain groups (p > 0.05) except at the tibialis anterior site (p = 0.02). The whiplash group demonstrated lowered cold pain thresholds compared to idiopathic and control groups (p < 0.03). For detection thresholds, the whiplash group showed elevated vibration (p < 0.04), heat (p < 0.02) and electrical (p < 0.04) thresholds at all upper limb sites compared to the idiopathic neck pain group and the controls (p < 0.04). Sensory hypoesthesia whilst present in chronic whiplash is not a feature of chronic idiopathic neck pain. These findings indicate that different pain processing mechanisms underlie these two neck pain conditions and may have implications for their management.