This study explored how caregiver-reported executive functioning domains, assessed by the BRIEF2 at baseline, predicted behavioral challenges reported by caregivers using the CBCL six months later. The sample included 94 youth with Down syndrome, aged 6 to 18 years. Results of hierarchical regression analyses revealed that, after controlling for the effect of IQ, working memory significantly predicted inattentive behaviors, inhibition significantly predicted rule-breaking behaviors, and both inhibition and emotional control significantly predicted aggressive and externalizing behaviors. After controlling for baseline behaviors, only working memory persisted as a significant predictor of inattentive behaviors measured six months later. The findings are discussed by referring to the relevant theories and research and providing clinical implications and recommendations for further studies.