In this study, a group of students with dyslexia were provided with an author-developed Hangul phonics program for 10 weeks. Each lesson was composed of five phonemic awareness activities and five phonics activities Well-trained teachers delivered lessons to students, individually, twice a week. A single-subject design was employed with the goal of investigating the effects of the intervention on students’ ability to spell. The PND results clearly revealed that the Hangul phonics intervention successfully improved spelling abilities of students with dyslexia. The authors also administered a series of standardized tests before and after the intervention that covered letter knowledge, phonological awareness, phonological processing, and phonological memory, in addition to spelling. The non-parametric t-test results for these measures showed that the Hangul phonics intervention not only improved students’ spelling skills but also their phonological awareness, phonological processing, phonological memory, and letter knowledge. Notably, this is the first Korean study bringing objective evidence of the effects of phonics intervention on letter knowledge and phonological processing skills. Since these skills are core deficits for dyslexic students, it is important to determine that Hangul phonics intervention can improve them for Koreans with dyslexia. Phonics intervention did not, however, improve composition skills. A previous study suggested that the effects of phonics intervention on composition skills become more palpable as intervention continues; the insignificant effect of phonics intervention on composition fluency in the current study may perhaps be due to the relatively short period of the intervention. Hangul phonics instruction generally does not appear in elementary curricula, and to prevent learning problems among many students, teachers must systematically and intensively implement phonics instruction. This paper also discusses concerns and solutions that arose regarding the implementation of phonics intervention as a regular school practice.