Holland Ronald Koeman was admitted to hospital with a heart problem on Sunday, the daily De Telegraaf reported on its website.
The 57-year-old was taken from his home by ambulance but after surgical intervention was in a stable condition, his wife Bartina told the newspaper.
Koeman has been the Dutch coach for just over two years and helped the country to qualify for Euro 2020, which has been postponed to next year due to the coronavirus pandemic.
The former international defender, who as a player won the European Cup with both PSV Eindhoven and Barcelona, managed Everton before he took charge of his native country's national team.