This article presents the use of conversation analysis (CA) in the context of sociocultural theory (SCT) driven research on L2 development, or CA-for-SCT. I focus specifically on the CA concept of action ascription as it applies to understanding the nature of mediation in interaction. I begin with an overview of the concept of action ascription before discussing the CA-for-SCT approach, and in particular Jim Lantolf's contribution to our understanding of the dialogic nature of graduated and contingent assistance in interaction. I then present several examples of interactions from SCT-based pedagogical enrichment programs to illustrate how mediation in interaction can be understood as action ascription. The discussion and conclusion then center on developing future research in this important domain.