Maria Guzun began working as a magistrate in 1996, at the Riscani District Court in Chisinău. Before that, she had acted as a senior consultant at the Supreme Court of Justice for two years. In 2008 Mrs. Guzun was appointed to the Court of Appeals, where she still is.

Maria Guzun is one of the judges responsible for the condemnation of Moldova at the European Court of Human Rights. She was part of a panel that removed a protection order in a case related to domestic violence. As a consequence, in 2013 the Strasbourg-based institution found that the Moldovan authorities tolerated family violence and awarded the plaintiff 17,150 euros.

The judge has been married to Ion Guzun, a judge at the Supreme Court of Justice, and their son works at the Chisinau City Court since 2016.