The present study is aim to how bilingual children used another language as well as their mother tongue was explained on the basis of Bernstein's code theory. For this purpose, spontaneously bilingual children were examined in their natural environment and explained according to the Berstein's code theory. It also emphasized the importance of bilingualism at an early age. In this study, a case study as one of the qualitative research methods was used. Two bilingual children were observed and the observations obtained were noted by researcher. The code switching in between two children was examined and compared according to the theory explained in the literature. According to the findings of the research one of the examples shows the positive effect of the use of code switching and the other shows the negative effect. The results of research has shown that the use of code switching, that is, allowing language switching, has a supporting role in children's acquisition of a new language.