jats:titleAbstract</jats:title> jats:pIn an increasingly multilingual world, empirical knowledge about the reciprocal influence between the mother tongue (L1) and a learner’s acquisition of foreign languages (FL) is crucial yet remains surprisingly scarce. This paper examines how an explicit focus on metacognitive strategy use within a FL (German) classroom impacts students’ development of writing strategies in the FL, and whether any such effects transfer to another FL (French) and/or to the L1 (English). Based on a quasi-experimental design, the study involved a two-phase intervention of strategy-based instruction primarily in the FL classroom and later also in the English classroom in a secondary school in England. Data were collected using writing strategy task sheets. Key findings indicate high levels of cross-linguistic transfer, both from one FL context to another and from FL – L1, evidenced especially by an improvement in the quality of students’ planning and a reduction in the number of errors. Findings support the development of a multilingual, strategy-based pedagogy for writing where L1 and FL teachers collaborate to encourage and facilitate connection-making across language contexts.</jats:p>