Research has yet to determine how much of the variance in sluggish cognitive tempo (SCT) symptom ratings is consistent across occasions, sources, and settings versus specific to occasion, source, and setting. Our first objective was to determine the amount of variance in SCT ratings that was consistent ( trait consistency) across three occasions of measurement over 12 months versus specific to the occasion ( occasion-specificity) with ratings by mothers, fathers, primary teachers, and secondary teachers of 811 Spanish children. Our second objective was then to determine the convergent validity for trait consistency and occasion-specificity variance components within and across settings. SCT ratings reflected mostly trait consistency for mothers, fathers, and primary teachers (less so for secondary teachers) with the convergent validity for trait consistency also being strong for mothers with fathers and for primary teachers with secondary teachers. Across home and school, however, convergent validity for trait consistency was low and even lower for occasion-specificity. SCT appears to be more trait-like rather than state-like, with similar levels of trait consistency across occasions and convergent validity within settings as attention-deficit/hyperactivity disorder (ADHD) symptoms in a prior study. However, SCT symptoms had slightly weaker convergent validity for trait consistency across settings relative to ADHD symptoms.