This study tested the efficacy of supplemental phonics instruction for 84 low-skilled language minority (LM) kindergarteners and 64 non-LM kindergarteners at 10 urban public schools. Paraeducators were trained to provide the 18-week (January-May) intervention. Students performing in the bottom half of their classroom language group (LM and non-LM) were randomly assigned either to individual supplemental instruction (treatment) or to classroom instruction only (control). Irrespective of their language status, treatment students (n = 67) significantly outperformed controls (n = 81) at posttest in alphabetics, word reading, spelling, passage reading fluency, and comprehension (average treatment d = 0.83); nevertheless, LM students tended to have lower posttest performance than non-LM students (average LM d = -0.30) and were significantly less responsive to treatment on word reading. When we examined the contribution of classroom phonics time to student outcomes, we found that the treatment effect on spelling was greater for students in lower phonics classrooms, whereas the treatment effect on comprehension was greater for those in higher phonics classrooms. Finally, when we examined LM students alone, we found that pretest English receptive vocabulary positively predicted most posttests and interacted with treatment only on phonological awareness. In general, pretest vocabulary did not moderate kindergarten LM treatment response. (Contains 6 tables and 2 figures.)