Background: Collaborative learning is widely applied in real-world classrooms while young learners still have challenges engaging in high-quality knowledge co-construction processes. Researchers suggested an individual preparation activity before collaboration. However, there remains a limited understanding of the role of individual preparation on students' collaborative learning. Method: Conducted in a fifth-grade English language class in a Singapore primary school, this study explored students' collaborative learning outcome and process under two conditions: individual preparation before collaboration (With-IP) and immediate collaboration (Without-IP) conditions. Student groups' collaborative argumentation artifacts were collected and coded. Process analysis was conducted to reveal the distribution and transitional pattern of students' verbal discussions and online collaboration behaviors. Findings: This study reveals that individual preparation (With-IP) significantly enhanced the quality of collaborative argumentation compared to no preparation (Without-IP), by fostering more idea elaboration, deeper engagement with content knowledge, and higher quality of arguments. However, the students were also found to make more coordination and regulation efforts in the With-IP condition than Without-IP condition. Contribution: This research underscores the role of individual preparation on collaborative learning processes and outcomes. This insight is pivotal for educators and practitioners in tailoring collaboration scripts to the objectives of classroom teaching and learning.