<![CDATA[Grounded in the Technological Pedagogical Content Knowledge (TPACK) framework, this action research examined how an English teacher's technological, pedagogical, and content knowledge shaped the use of WhatsApp as a virtual learning medium to improve the narrative writing skill of eleventh-grade students at a public senior high school in Tanimbar Selatan, Maluku Province, Eastern Indonesia, during pandemic-driven online instruction. Thirty students participated across two action research cycles of planning, implementation, observation, and reflection, in which the teacher's knowledge of WhatsApp's features, of narrative structure and the simple past tense, and of staged, scaffolded instruction was enacted through instructional videos, graphic organizers, sequential pictures, and emojis distributed and monitored via WhatsApp. Data were collected through a teaching journal, observation checklists, a Likert-scale questionnaire administered once at the end of the second cycle, and pre- and post-writing tests scored with an analytic rubric. Mean writing scores rose from 53.83 (SD = 12.43) at pre-test to 71.33 (SD = 10.98) after Cycle 1 and 81.83 (SD = 6.50) after Cycle 2, with the proportion of students scoring Good or Excellent increasing from 26.7% to 100% over the same period. Students also reported positive perceptions of the WhatsApp-mediated activities, including motivation, confidence, and progress in vocabulary and sentence construction, with most items receiving over 90% agreement on a questionnaire administered once at the end of the intervention. As an action research case rather than a controlled experiment, the study cannot isolate the precise contribution of WhatsApp or of any single TPACK domain; instead, the findings suggest that narrative writing improved alongside an increasingly structured enactment of the teacher's TPACK, through staged planning, implementation, and monitoring, rather than through the application alone. Implications for strengthening EFL teachers' TPACK in similarly under-connected regional settings are discussed.]]>
