Code switching has been studied predominantly in adults and children over the age of three. Research in younger children is scarce. The present study was conducted as a single case study on the babbling of a one-year-old who is being raised bilingually (Spanish/English). The aim of the study was to determine whether the baby babbled differently depending on the language of the interlocutor and the context. The interlocutors involved follow a one person - one language strategy of interaction with the baby. The child's spontaneous speech was recorded during interaction with his mother (English) and with his grandmother (Spanish). So as to make the contexts as clear-cut as possible, the recordings took place while the child was alone with each interlocutor at their respective homes. Samples were recorded at the age of 1:2, 1:3, and 1:4 in order to check whether the phenomenon under investigation varied as the child approached the one-word stage. The utterances were transcribed by a bilingual teacher specialized in phonetics. The data is analysed and the use of Spanish/English is discussed from a sociolinguistic perspective.