Background: Anxiety disorders increase the risk of onset of several ageing-related somatic conditions, which might be the consequence of accelerated cellular ageing. Aims: To examine the association between anxiety status and leukocyte telomere length (LTL) as an indicator of cellular ageing. Method: Data are from individuals with current (n = 1283) and remitted (n = 459) anxiety disorder, and controls (n = 582) with no psychiatric disorder from the Netherlands Study of Depression and Anxiety. We determined DSM-IV anxiety diagnoses and clinical characteristics by structured psychiatric interviews and self-report questionnaires; LTL was assessed using quantitative polymerase chain reaction and converted into base pairs (bp). Results: Patients in the current anxiety group (bp = 5431) had significantly shorter LTL compared with the control group (bp = 5506, P = 0.01) and the remitted anxiety group (bp = 5499, P = 0.03) in analyses adjusted for sociodemographics, health and lifestyle. The remitted anxiety group did not differ from the control group (P = 0.84), however, time since remission was positively related with LTL. Furthermore, anxiety severity scores were associated with LTL in the whole sample, in line with a dose-response association. Conclusions: Patients with current - but not remitted - anxiety disorder had shorter telomere length, suggesting a process of accelerated cellular ageing, which in part may be reversible after remission.