The main aim of the book is to investigate the facilitative role of learners’ native language (L1) in raising their consciousness of foreign language (L2) grammatical structures. The literature review focuses on selected second language acquisition theories which explain the role of the different conceptualizations of consciousness in L2 learning, on the position of grammar in contemporary L2 pedagogy, with special regard to grammatical consciousness-raising, and on theoretical and empirical perspectives on the functions of learners’ L1 in L2 learning and teaching. The empirical part of the book presents the methodology and results of a mixed-methods study conducted on low-proficiency adult learners of L2 English with the aim of exploring the role of their L1 (Polish) in promoting the noticing, understanding, and explicit knowledge of L2 grammatical structures. The results revealed a number of significant functions of the L1 in enhancing the participants’ consciousness of the targeted structures, evidenced in the use of mental strategies (i.e. translation, cross-linguistic comparisons, making inferences, metalinguistic reasoning, etc.), in the results of tests, and in opinions expressed in debriefing interviews.