This paper will cover the topic of bilingualism in preschool-aged children. The paper contains data collected by reviewing and researching texts on the topic of bilingualism in books, scientific and professional articles and on the Internet. Language, as an indispensable factor in human communication, plays a very important role in human life. Bilingualism is an increasingly common phenomenon nowadays, complex and diverse, and its simplest definition is that it implies using and mastering two languages. The purpose of this paper is to introduce the reader to the phenomenon of bilingualism in children of early and preschool age. The paper focuses not only on the definition of bilingualism, but also on the types of bilingualism as well as speech development and language acquisition in children in the context of bilingualism. The role of adults in the development and upbringing of the child is essential. The influence of parents as well as the influence of educators in kindergartens is extremely important when it comes to encouraging bilingualism. The attitude towards bilingualism was much more unfavorable in the past than it is today and the negative effects that it can have were emphasized as well. According to many recent studies bilingualism has multiple advantages and its positive influence on the child’s development is more evident these days.