Becoming a history teacher requires the integration of pedagogical knowledge, pedagogical content knowledge, and content knowledge. Because the integration of knowledge from different disciplines is a complex task, we investigated prompted learning journals as a method to support teacher students' knowledge integration. Fifty-two preservice history teachers participated in the experimental study. They read a text about a historical event, a text about teaching history, and a text about cognitive learning processes. Then they wrote a learning journal entry about the three texts. To support the journal writing, the participants in the experimental condition received four integration prompts, whereas the participants in the control condition received no prompts. In the prompted condition, the students engaged more often in integration strategies at the cost of rehearsal and organization strategies. Rehearsal and integration strategies predicted students' recall of knowledge and their ability to evaluate learning tasks. Integration strategies as elicited in the journals predicted preservice teachers' performance when designing a learning task for history education. In solving this task, the prompted preservice teachers used the information from the three texts in a more balanced way than the unprompted students who strongly focused on content knowledge. The study illustrates the potentials of learning journals as a method to support knowledge integration in history teacher education.