Flyweight Adams secured a technical knockout victory over Dutch rival Abbygail Deekman to secure progress to the semi-finals in Hungary.
Lightweight Natasha Jonas and featherweight Lisa Whiteside are also guaranteed medals for Great Britain after unanimous quarter-finals wins over Poland's Karolina Graczyk and Karolina Michalczuk respectively.
“The time since winning the Olympic gold has been an absolutely fantastic experience but it is now time to get back to business," said Adams.
"There are still so many things I want to achieve as a boxer and defending my EU title is the start of the next phase of my career.”
- Sports & Recreation
- Natasha Jonas
- Karolina Michalczuk