It is known that some languages, such as those which are minority languages in the countries of origin, tend to be hidden in some educational contexts with monolingual practices. Although the relatively new field of (instructed) third language (L3) acquisition has developed within the recent years as a field on its own, it has not yet had much impact on mainstream pedagogical approaches. Similarly, even if teachers possess knowledge about multilingual pedagogies, applying it into classroom practices remains a challenge. This is taken as a starting point to fill in the existing gap of how theory can inform L3 teaching and vice versa. Starting from the existing results and non‐results, this entry includes accounts of the current state of the art theory and practice on predicting possible transfer phenomena, guidelines for methods and interventions that take into consideration the role of transfer in instructed third language acquisition (IL3A).