Administrative health databases are valuable sources of data for conducting research including disease surveillance, outcomes research, and processes of health care at the population level. There has been limited use of administrative data to conduct studies of pediatric rheumatic conditions and no studies validating case definitions in Canada. We report a validation study of incident cases of juvenile idiopathic arthritis in the Canadian province of Nova Scotia. Cases identified through administrative data algorithms were compared to diagnoses in a clinical database. The sensitivity of algorithms that included pediatric rheumatology specialist claims was 81-86%. However, 35-48% of cases that were identified could not be verified in the clinical database depending on the algorithm used. Our case definitions would likely lead to overestimates of disease burden. Our findings may be related to issues pertaining to the non-fee-for-service remuneration model in Nova Scotia, in particular, systematic issues related to the process of submitting claims.