<p>As an altruistic and prosocial construct, empathy is viable in promoting interpersonal dynamics and in inducing positive changes in learners’ behaviors. However, its role in mediating peer collaboration and promoting writing achievements remains largely unexplored in the studies of collaborative writing. To address this gap, this mixed-method study involving 18 EFL learners (five males and 13 females) in Taiwan investigated the role of empathy in dyadic collaborative writing and its impact on learners’ writing performance over two semesters. The age of the learners ranged from 19 to 23, and their English proficiency was intermediate to high-intermediate. Seven research tools were adopted for data triangulation. The results revealed significant gains in empathetic understanding and collaborative writing but stagnation in communicating empathy. The study identified five influencing factors: internal/external interferences, perceived self-image, mutual familiarity, learners’ attitudes/problem-solving skills, and responses to collaborative writing. The interplay of these five factors led to different levels of empathetic collaboration and transformation in the learners. The findings revealed the complexity and variation of collaborative writing over time and two little-reported areas in collaborative writing: (1) obstacles to the development of empathy: external interference and perceived negative self-image, and (2) mutual familiarity playing a dual role: a mediator and inhibitor. Pedagogical implications concerning the promotion of learners’ empathy and collaboration in the EFL writing classroom are presented, and future research direction is suggested.</p>