The present study aimed to predict responsiveness to a sustained two-phase reading and spelling intervention with a focus on declarative and procedural learning respectively in 122 second-grade Dutch children with dyslexia. We related their responsiveness to intervention to precursor measures (phonological awareness, rapid automatized naming ability, letter knowledge, and verbal working memory) and related word and pseudoword reading and spelling outcomes of the sustained intervention to initial reading and spelling abilities, and first-phase, initial treatment success. Results showed that children with dyslexia improved in reading accuracy and efficiency and in spelling skills during the two phases of the intervention although the gap with typical readers increased. In reading efficiency, rapid automatized naming, and in reading and spelling accuracy phoneme deletion predicted children's responsiveness to intervention. Additionally, children's initial reading abilities at the start of the intervention directly (and indirectly, via initial treatment success, in reading efficiency) predicted posttest outcomes. Responsiveness to intervention in spelling was predicted by phoneme deletion, and spelling at posttest was indirectly, via initial treatment success, predicted by children's initial spelling abilities. Finally, children's initial treatment success directly predicted reading efficiency and spelling outcomes at posttest. © 2019 The Authors Dyslexia Published by John Wiley & Sons Ltd.