A meta-analysis was conducted on the effects of computer-supported early literacy interventions (strict phonological awareness training, combined phonological awareness and letter training, and use of e-books) on phonological-awareness (syllabic awareness, word blending, rhyme, phoneme awareness) and reading-related skills (concept about print, letter knowledge, decoding, spelling) across different languages in preschool and kindergarten since 1995. A total of 59 studies were identified with a total amount of 339 effect sizes, involving 6786 preschool and kindergarten students. A multilevel approach was followed to estimate the average effect size and to examine the moderation of effects. On average, a small positive effect size of 0.28 with 95% CI (0.21, 0.35), was evidenced across treatments and across outcome measures. Large variation in effect sizes was observed between studies and especially between comparisons within studies. If the intervention was part of an integrated learning system in the classroom, the effects were better. The present analysis also shows the importance of methodological rigor of study designs being used in that effect sizes were higher in cases of absence of randomization and comparisons with classroom teaching as usual instead of an active control group.