Hailing from Žiar nad Hronom in Slovakia, the defender began his professional career at MŠK Žilina. He made his first appearance in the Slovak league on 27 March 2012, at the age of 17 years and 49 days. He completed the 2011-2012 season and started the 2012-2013 season with MŠK Žilina before being loaned to Zlaté Moravce to gain more experience. He continued his progression by moving to Serie A, joining Sampdoria. He made his debut for the new club in a home victory against Lazio on 24 April 2016, and finished the season as the youngest defender to make at least 35 appearances in Serie A.
He then caught the attention of the biggest teams in Italy and decided to join Inter Milan in 2017. He had a highly successful first season with Inter Milan, establishing himself as one of the best defenders in the league. With the arrival of Stefan de Vrij, he formed one of Serie A's strongest defences, winning the Italian championship in the 2020-2021 season. After going through all the stages with Inter Milan, where he even became captain, he signed for Paris Saint-Germain as a free agent at the age of 28 during the summer transfer window of 2023.
