Sluggish cognitive tempo (SCT) is characterized by excessive daydreaming, slowed thinking, and mental confusion and ‘fogginess’. A growing body of research supports the empirical differentiation of sluggish cognitive tempo (SCT) from the inattentive (IN) behaviors that characterize attention-deficit/hyperactivity disorder (ADHD). Further SCT and IN are uniquely associated with clinical correlates across academic, social, and emotional domains; however, there is limited understanding of how neuropsychological functioning contributes to SCT and/or IN behaviors. The two broad domains of neuropsychological functioning that have been most frequently examined in relation to SCT behaviors are processing speed and executive functions (EF). The present study tested whether EF and processing speed measured when children were on average age five years were predictive of teacher-rated IN and SCT behaviors in 1st – 3rd grades. Participants included 1,022 children from the Family Life Project, an ongoing prospective longitudinal study of child development in low-income, non-metropolitan communities. EF and processing speed uniquely made independent contributions to the prediction of IN and SCT. In secondary analyses that focused on specific facets of EF and processing speed, inhibitory control and working memory abilities predicted lower IN but not SCT behaviors, whereas slower processing speed significantly predicted both greater SCT and IN behaviors. These results are discussed as they inform developmental models of SCT and IN.