The purpose of this study was to examine the effects of Build a Word-Easy Spelling with Phonics, an electronic application of the word box intervention, on the acquisition, maintenance, and generalization of letter-sound correspondences for Learners of English as an Additional Language (LEALs). A single-subject multiple probe experimental design across five kindergarten LEALs. Students' acquisition and maintenance of letter-sound correspondences were measured by the number of correct letter-sound correspondences identified in trained words and the number of trained words read correctly. Generalization measures involved identifying letter-sound correspondences in untrained real and nonsense words and a spelling task. Visual analysis and TAU-U calculations were used to examine intervention effects. Results demonstrate that the intervention Build a Word-Easy Spelling with Phonics substantially improved the acquisition, maintenance, and generalization of letter-sound correspondences for the five LEALs. This study extends research on the effects of systematic phonics interventions for LEALs. Implications for practice are discussed.