In contrast to the traditional cognitive view of writing strategies, this study explores English as a foreign language (EFL) learners' writing strategy use within the Activity Theory framework, adding to the growing body of writing strategy research and sociocultural research on writing and second language acquisition (SLA). Drawing on data collected from interviews, stimulated recall, and process logs completed by two proficient English majors in a Chinese university, the study investigates how these two learners strategically mediated their writing processes with diverse resources and identifies four types of writing strategies, namely, artifact-mediated, rule-mediated, community-mediated, and role-mediated strategies. Subcategories are specified within each category to further explicate the learners' strategy use. These categories and subcategories, though by no means exhaustive, reconceptualize writing strategies from a sociocultural perspective. Moreover, contradictions in strategy use, writers' agency, writing goals, and interactions between strategies are discussed. Finally, the study suggests implications for writing instruction and future directions of writing strategy research. (Contains 1 table and 1 figure.)