Acupuncture is widely used by patients with neck pain, but there is a lack of information about its effectiveness in routine medical care. The aim was to investigate the effectiveness of acupuncture in addition to routine care in patients with chronic neck pain compared to treatment with routine care alone. We performed a randomized controlled multicentre trial plus non-randomized cohort in general practices in Germany. 14,161 patients with chronic neck pain (duration >6 months). Patients were randomly allocated to an acupuncture group or a control group receiving no acupuncture. Patients in the acupuncture group received up to 15 acupuncture sessions over three months. Patients who did not consent to randomization received acupuncture treatment. All subjects were allowed to receive usual medical care in addition to study treatment. Neck pain and disability (NPAD Scale by Wheeler) after three months. Of 14,161 patients (mean age 50.9+/-13.1 years, 68% female) 1880 were randomized to acupuncture and 1886 to control, and 10,395 included into the non-randomized acupuncture group. At three months, neck pain and disability improved by 16.2 (SE: 0.4) to 38.3 (SE: 0.4); and by 3.9 (SE: 0.4) to 50.5 (SE: 0.4), difference 12.3 (p<0.001) in the acupuncture and control group, respectively. Treatment success was essentially maintained through six months. Non-randomized patients had more severe symptoms at baseline and showed higher neck pain and disability improvement compared to randomized patients. Treatment with acupuncture added to routine care in patients with chronic neck pain was associated with improvements in neck pain and disability compared to treatment with routine care alone.