Previous research showed that short-term second language training modulates children's brain responses to language processing. However, little is known about whether short-term training from language-immersion apps would have the same effect on young children's neural processing of a newly learnt language. We examined the auditory event-related potentials generated by two groups of 3- to 5-year-old children (total N = 32; 14 male, 18 female; mean age = 49.6 months, SD = 6.0 months), in response to known and unknown non-native language words. The 'known' word stimuli were previously exposed to the children via either the ELLA language immersion applications ('ELLA' group) or flash cards ('FLASH' group). Electroencephalography data were analysed within early (200-300 ms) and late (400-600 and 600-800 ms) time-windows, to determine the main and interaction effects of group (ELLA vs. FLASH) and condition (KNOWN vs. UNKNOWN). We found that the early positive potential (of both groups) for the known words was significantly larger than that for the unknown words. Further, the early negative potential of the apps group was significantly larger than that of the flash card group. Our study showed that short-term training with language-immersion apps modulates language processing in preschool children's brains differently compared to digital flash cards.