Background. The ability to understand idiomatic expressions begins to develop at an early age. However, such skill is not achieved within the same age and at the same pace in children speaking different languages. Objective. This study assesses comprehension of idiomatic expressions by Russian-speaking monolingual children aged 4 to 12 and monitoring the age dynamics of figurative language understanding. Design. 80 children were split in 4 age groups balanced for gender and level of formal education. The participants were asked to identify the correct non-literal meaning of 10 idioms. For each idiomatic expression, children heard three potential interpretations (one correct, and two incorrect ones of which one was literal while the other was overtly wrong). Results. Age-related differences were analysed by performing a series of univariate ANOVAs. These analyses showed that already at preschool age children begin to understand some kinds of idiomatic expressions and that such ability slowly develops throughout childhood. Interestingly, until the age of 6 children predominantly interpreted idioms literally. By the age of 7 their ability to correctly understand the non-literal meanings of idiomatic expressions enhanced significantly until it reached a plateau around the age of 12. Conclusion. The results of the study are in line with those found for children speaking other languages. The findings are interpreted in light of recent theories of language and cognitive development. Potential limitations of the study are also discussed.