Intracoronary acetylcholine (ACh) provocation test is useful to diagnose vasospastic angina. However, paroxysmal atrial fibrillation (AF) often occurs during intracoronary ACh provocation test, leading to disabling symptoms. The aim of this study was to investigate the incidence and predictors of paroxysmal AF during the test. A total of 377 patients without persistent AF who underwent intracoronary ACh provocation test were included. Paroxysmal AF during ACh provocation test was defined as documented AF on electrocardiogram during the procedure. There were 31 patients (8%) with paroxysmal AF during the test. Of these, 11 (35%) required antiarrhythmic drugs, but none received electrical cardioversion. All of them recovered sinus rhythm within 48 h. At procedure, paroxysmal AF occurred mostly during provocation for the right coronary artery (RCA) rather than for the left coronary artery (LCA) (90 vs. 10%). Multivariate logistic regression analysis demonstrated that a history of paroxysmal AF (OR 4.38 CI 1.42–13.51, p = 0.01) and body mass index (OR 0.88 CI 0.78–0.99, p = 0.03) were independent predictors for occurrence of paroxysmal AF during intracoronary ACh provocation test. In conclusions, paroxysmal AF mostly occurs during ACh provocation test for the RCA, especially in patients with a history of paroxysmal AF and lower body mass index. It may be better to initially administer intracoronary ACh in the LCA when the provocation test is performed.