In the teaching of sign languages as foreign languages (FLs), teachers instruct learners in vocabulary and conversational grammar. In doing so they frequently notice that some learners are able to learn and produce vocabulary and use correct grammar, whereas others struggle. For a better understanding of learners' learning processes and their own pedagogical approaches, FL teachers turn to research studies on the teaching and learning of FLs. However, those studies are often largely inapplicable to their in-classroom practices. To resolve this problem, this article proposes and explicates teacher-as-researcher as a research paradigm for teachers' pedagogical development to bring about improved learner outcomes.