Building on social constructivist theory, this case study analyzed how pre-service secondary teachers co-constructed knowledge and expressed socioemotional interaction in online breakout rooms during a collaborative task. Video data was analyzed by content and interaction analysis. There was more higher-level knowledge construction than in most studies from asynchronous settings. Active listening and humor were thoroughly present. Talk about personal experiences occurred at both lower and higher levels of thinking. The teacher educator's visits to the breakout rooms and purposeful dissonance affected knowledge co-construction and socioemotional interaction. The findings will help in designing high-quality online and blended teacher education.