This article deals with the problem of Spanish-Russian bilingualism among children, gives a brief theoretical description of the main notions connected with the bilingualism. The central notion is code-switching. It is one of the forms of language interaction in written and verbal bilingual speech. The Carol Myers-Scotton’s conception, so-called Matrix Language Frame model, is used as thetheoretical basis of this article. The recordings of one bilingual child’s idiolect are used as a practical basis for this article. The bilingual’s parents (Russian mother and Spanish father) talk to the child using the concept “One Person – One Language” which means that each parent talks to the child in their native language only. Due to this type of communication, the child automatically creates his own original bilingual phrases, most of which are included in this article.