Purpose This study aims to apply and extend the theory of planned behavior (TPB) to predict intention to take a COVID-19 vaccine. Design Cross-sectional. Setting Online. Sample Adult US residents recruited from Amazon Mechanical Turk ( n = 172). Measures Intention to take a COVID-19 vaccine (outcome variable), demographic variables (predictors), standard TPB variables (perceived behavioral control, attitude, and subjective norm; predictors), and non-TPB variables (anticipated regret, health locus of control, and perceived community benefit; predictors). Analysis Hierarchical linear regression predicting intention to take a COVID-19 vaccine, with demographic, standard TPB, and non-TPB variables entered in regression models 1, 2, and 3, respectively. Results The extended TPB model accounted for 72.5% of the variance in vaccination intention ( p < .001), with perceived behavioral control ( β = .29, p < .001), attitude ( β = .23, p = .043), and perceived community benefit ( β = .23, p = .020) being significant unique predictors. Conclusion Despite the relatively small and non-representative sample, this study, conducted after COVID-19 vaccines were widely available in the USA, demonstrated that perceived behavioral control was the most robust predictor of intention to take a COVID-19 vaccine, suggesting that the TPB is a useful theoretical framework that can inform effective strategies to promote vaccine acceptance.