ObjectivesDentists' Medicaid participation is a critical factor affecting dental care access for Medicaid beneficiaries. An important gap in existing literature is the variation in participation across Medicaid dental Managed Care Organizations (MCOs) in states with more than one. This study examined the variation in participation overall and in predictors of dentist participation between two MCOs in Iowa's Dental Medicaid program.MethodsData were obtained from a survey of Iowa private practice dentists (n = 1256). Responding general dentists (n = 497) were included in the final analytic sample. Univariate, bivariate, and multivariable logistic regression analyses were conducted to examine demographic and practice characteristics associated with dentist participation (acceptance of new Medicaid patients) between MCOs and by age category.ResultsAmong respondents, the proportions accepting new adults with Medicaid were 26% (MCO 1) and 7% (MCO 2); for children, they were 40% (MCO 1) and 11% (MCO 2). For adults, dentists who were too busy (MCO1) and solo practice dentists (MCO2) were positively significantly associated with the acceptance of new patients. For children, group and rural practice dentists, as well as dentists who worked <32 h/week were positively significantly associated with acceptance of new patients with MCO1.ConclusionsThere was considerable variation in dentist‐reported acceptance of new adult and child Medicaid patients, and in the factors affecting acceptance of new patients between MCOs in Iowa dental Medicaid. Future studies of Medicaid participation should consider variations by MCO in states with more than one dental MCO so as not to miss important factors affecting Medicaid participation.