Normal jaw function involves muscles and joints of both jaw and neck. A whiplash trauma may disturb the integrated jaw-neck sensory-motor function and thereby impair chewing ability; however, it is not known if such impairment is present shortly after a neck trauma or develops over time. The aim was to evaluate jaw function after a recent whiplash trauma. Eighty cases (47 women) were examined within 1 month after a whiplash trauma and compared to 80 controls (47 women) without neck trauma. Participants completed the Jaw disability checklist (JDC) and Neck Disability Index (NDI) questionnaires and performed a 5-minute chewing test. Elicited fatigue and pain during chewing were noted, and group differences were evaluated with Fisher's exact test and Mann-Whitney U-test. Compared to controls, cases had higher JDC (P < .0001) and NDI scores (15% vs 2%, P < .0001), and reported more fatigue (53% vs 31%, P = .006) and pain (30% vs 10%, P = .003) during the chewing test. Cases also had a shorter onset time for fatigue and pain (both P = .001) Furthermore, cases reporting symptoms during chewing had higher JDC and NDI scores compared to cases not reporting symptoms (both P = .01). Symptoms mainly occurred in the trigeminal area for both groups, but also in spinal areas more often for cases than for controls. Taken together, the results indicate that jaw-neck sensory-motor function is impaired already within 1 month after a whiplash trauma. The association between neck disability and jaw impairment underlines the close functional relationship between the regions, and stresses the importance of multidisciplinary assessment.