Objectives: Assessing parental attributions can be challenging given the reticence of some caregivers to report information that may be considered controversial or pejorative. To address this issue, recent efforts have focused on expanding existing parenting assessment batteries to include implicit measures. One of the most common methods for implicit assessment, the Implicit Association Test (IAT), had not yet been adapted to assess parental attributions. Two studies evaluated the psychometric properties (including convergent, concurrent, incremental, and predictive validity) of the novel Noncompliance IAT (N-IAT). Methods: Study 1 included a low-risk sample of mothers (N = 60) of preschoolers. Study 2 included a diverse and higher risk sample of mothers and fathers who were assessed at three time points: immediately before the birth of their first child (N = 202 women; N = 144 male partners) and then 6 and 18 months after the birth. Results: Findings from both studies supported the utility of the N-IAT as a measure of implicit parental attributions. The N-IAT demonstrated evidence of convergent and concurrent validity (e.g., significant correlations with explicit attribution measures and with measures of parenting) in both studies. The longitudinal design of Study 2 allowed for the evaluation of incremental and predictive validity; N-IAT scores before childbirth predicted later N-IAT scores, with indications that the N-IAT could demonstrate incremental validity related to child abuse risk. Study 2 also demonstrated moderate test stability for mothers and fathers. Conclusions: These results suggest that the N-IAT may be a helpful adjunct to assessments of parental attribution.