The Attention, Relevance, Confidence, and Satisfaction (ARCS) model provides a basis for integrating motivational dynamics and technological affordances into the design and implementation of instructions to maintain learner motivation and interest. Little attention has been paid to this potential in teaching the complex and often demotivating skill of second/foreign-language (L2) writing. This study examined synergistic effects of ARCS-flipped teaching on Iranian English-as-a-foreign-language (EFL) learners' expository-writing performance and motivation. Participants were 59 EFL learners in two intact classes who were assigned to two groups. In the experimental group, the ARCS model was integrated into the flipped writing course. Hybrid Edmodo plus face-to-face learning spaces were used to implement ARCS strategies alongside the instruction. In the control setting, the model was implemented in the face-to-face writing course. A data-triangulation approach, comprising writing tasks, the Course Interest Survey, and semi-structured interviews was adopted. ANCOVA results showed that the ARCS-flipped group outperformed the face-to-face group in their writing performance. Furthermore, the motivational-technological synergy led to more increased learner motivation. Learners' retrospective perceptions revealed that the flipped features of flexibility, learner-centeredness, relaxed environment, interactivity seamlessness, and collaboration appealed to the learners' varied time-space preferences, which, in turn, stimulated their motivation, learning engagement, and writing performance.