Sense-making is the process by which people give meaning to their collective experiences. Sense is viewed as knowledge, and the environment in which the sense is made is interconnected with communication effectiveness. Considering the critical role of sense-making in the learning process, scholars have emphasised the significance of providing interactive learning environments for students' effective learning. By employing a modified version of Dervin's sense-making theory, this qualitative case study explores the nature of students' sense-making processes in a peer self-founded online learning group without teacher involvement. The study analysed online Chat logs generated by 30 English language learning students from a secondary school in China. The Chat logs were students' discussions on a module of English writing: "Read and then write". The researchers made meaning of the students experiences through their dialogue and interaction, which revealed the essence of a sense-making process: gap facing, gapdefining, gap bridging and gap bridged. The observations were followed with students' interviews held to identify the factors contributing to an interactive learning environment for effective sense-making. The study found that the affordances of an interactive environment impact the communication outcomes through the interactional achievement in the sense-making process.