Few studies have examined the longitudinal association between sluggish cognitive tempo (SCT) symptoms and internalizing symptoms, and no study has examined the potentially bidirectional associations between SCT and internalizing symptoms. The present study used a short-term longitudinal design to examine the directionality of the associations between SCT, depressive, and anxious symptoms in children. Teachers of 188 children in 1st to 6th grades (6-13 years of age; 47% boys) provided ratings of children's SCT, anxiety, and depressive symptoms in the fall school semester (T1) and again 6 months later (T2). Children in 3rd to 6th grades (n = 133) provided ratings of anxiety and depressive symptoms at both time points. Cross-lagged panel models examining the longitudinal associations between SCT, anxiety, and depressive symptoms were conducted controlling for sex and grade, with separate models for teacher- and child-reported internalizing symptoms. SCT symptoms at Time 1 (T1) predicted increased depressive symptoms at T2, with findings consistent across teacher-rated depression and child-rated depression. Depression at T1 did not predict SCT at T2. SCT symptoms at T1 also predicted increased teacher-rated anxiety at T2 but not child-rated anxiety. Finally, child-rated anxiety at T1 predicted increased SCT at T2. Findings from this study provide the first evidence that SCT symptoms predict subsequent depressive symptoms and not the reverse. Associations between SCT and anxiety are more nuanced, with results differing based on the informant. Additional studies are needed to replicate and extend these findings across longer developmental periods with more time points and to examine mechanisms of the associations between SCT and internalizing symptoms in children.