This exploratory case study investigated an experienced second language writing instructor's written feedback practice in an ESL freshman composition class. The purpose of the research was to explore and examine contextual factors and their impact on instructor written feedback practices in order to provide situated descriptions of relationships between written feedback practices and contextual factors. Data were collected from one experienced ESL writing instructor and one ESL writer in a variety of forms: surveys, interviews, a stimulated-recall task, classroom and instructor-student conference observations, instructional materials, and student written product. The study found that the instructor's decision-making in selecting specific feedback forms was guided by a number of written feedback practice principals in conjunction with other contextual factors such as the instructorperceived level of students' writing proficiency, the availability of writing conference, the nature of writing issues, students' writing performance in the previous writing assignments, lesson history, and knowledge about effective feedback practice. The study suggests L2 writing instructors' written feedback decisions are the product of different combinations of multiple-contextual factors and the nature of the written feedback practice principles is a task-specific manifestation of teacher cognition specifically configured for written feedback practice.