Rheumatoid arthritis (RA) and antisynthetase syndrome (ASS) are distinct clinical syndromes, and their co-occurrence is rarely encountered. The authors report the case of a 56-year-old female patient with RA of 3 years duration who suddenly developed ASS, and include a review of the literature. The patient was diagnosed with ASS based on; positivity for anti-histidyl-tRNA synthetase (Jo-1) antibody, interstitial lung disease, polyarthritis, and mechanic's hands. High-dose corticosteroid and pulse intravenous cyclophosphamide were used to control the ASS. This case demonstrates that ASS should be considered during clinical presentations due to its potential overlap with RA.