Despite the increasing number of studies on the specifics of Lithuanian spoken by expats, there’s still a lack of more extensive, large-scale research on the peculiarities of the Lithuanian language obtained in an environment where a different language is spoken. To that end, we conducted a study aimed at identifying the lexical and grammatical features of the Lithuanian language as they’re acquired in an English-speaking environment. The material was collected in four Lithuanian language schools based in London from 100 children aged 4-9. All of the children lived in London and attended private Lithuanian schools (~3-6 hours per week), learned their native language from their parents, were born in the United Kingdom, or moved there at the age of 1. During the experiment, the participants were asked to produce a narrative using a set of six pictures (Hickmann 2003; Gagarina et al. 2012). The narratives were recorded using a voice recorder, transcribed and morphologically annotated for an automatic analysis of narrative language using CHILDES (MacWhinney 2000) software. This study is the first to focus on the native language of children living in a bilingual environment, its productivity, lexical diversity, morphology, and syntax. The present article discusses several grammatical aspects of the Lithuanian language acquired as the mother tongue in an English-speaking environment – changes in inflection, as well as differential object marking, coordination and control, which often cause difficulties to children. An analysis of the material showed that the Lithuanian language inflection system of bilingual children can be acquired appropriately, regardless of the fact that in some children, the process may take as many as five or six years. Both younger and older children tend to simplify inflection, which leads them to inflect non-productive paradigm or less usual nouns in accordance with productive paradigms.[...]