While acquisition of more than one language from birth is a relatively common phenomenon, whether children under two years of age use their languages in a differentiated manner has not yet been established. The current study investigates the pragmatic differentiation of a child who lives in Australia and was acquiring two minority languages, German and Japanese, from his parents (German father; Japanese mother) who were following the one-parent, one-language principle. A maternal diary was kept from when the child was born, and the child's interactions with each parent were video-taped from 1;4 to 1;9. It was found that the child used two languages in a differentiated manner throughout the observed period. Several factors such as child's lexicon, habitual language use, parental discourse style and language dynamics surrounding child were investigated and all were found to affect the child's language choice. The child's early pragmatic differentiation provides support for the view of two-system hypothesis.