Previous research has established the important role of selfregulation in supporting school readiness and academic learning. However, most of the research has not included examinations of the relation between early writing and self-regulation, although writing is an academic skill that also contributes to school readiness. Therefore, the purpose of this study was to explore the associations between self-regulation and early writing as children transitioned from preschool to first grade. Two groups of children were followed longitudinally. Group 1 (n = 171) was followed from preschool to kindergarten to Grade 1, and Group 2 (n = 196) was followed from a first year of preschool (Preschool 1) to a second year of preschool (Preschool 2) to kindergarten. Writing assessments included tasks at the word, sentence, and discourse levels. Self-regulation was measured using the Heads-Toes-Knees-Shoulders task. Writing and self-regulation were stable across the early years. Writing achievement was concurrently related to and significantly predicted later self-regulation. Self-regulation was concurrently associated with writing achievement but did not predict later writing achievement. Structural equation modeling results indicated that writing was a significant predictor of longitudinal change in selfregulation from preschool to kindergarten. The bidirectional relations between self-regulation and writing achievement were not supported by the data. Implications of the findings and future directions are discussed, including the effect of task demands in understanding relations between self-regulation and academic skills. (c) 2022 Elsevier Inc. All rights reserved.