This book fills an existing gap in the field of third language acquisition (L3A) by bringing together theoretical, empirical, and practical accounts that contribute to informed teaching practices in multilingual classrooms. The volume is organised into three sections that focus on prominent syntactic transfer models in the field of L3A and together provide insights into the interplay of the influences of prior languages in L3 syntax and how we can enrich the practical field of instructed L3 acquisition. Part I includes original papers dealing with new developments of existing theoretical models on syntactic transfer in L3A and Part II consists of empirical studies testing existing models from different perspectives (formal, lexico-functional, and neurocognitive). Following these two sections, Part III discusses how theory can inform practices for L3 learning and teaching. This concise compilation brings to light innovations, not only in terms of theoretical refinements and practical implementations, but also in offering an impressive range of language combinations. This book is intended to act as a unique resource for scholars, applied linguists, language educators, both novices and experts alike, in and beyond the field of L3A.