Applying the single case analysis methodology, this study investigates how a peer tutee demonstrated his understanding of his peer tutor’s advice by using a particular type of formulation, response formulations to advice, to negotiate the pair’s participation framework in second language (L2) online peer tutorials. Although the tutor initially held the floor more often during the verbal interaction in the online tutorial, the tutee was able to move from peripheral to fuller participation by offering response formulations to advice. Two types of response formulations to advice were identified: (1) expressing the gist of the tutor’s advice to indicate direct comprehension, and (2) constructing an upshot to add a new viewpoint to the previous utterance by conveying unstated information (e.g., offering an account of what was not discussed in previous discourse). The tutee’s response formulations to advice provided the tutor with an opportunity to access the tutee’s L2 knowledge and thereby offer more mediation to enhance the tutee’s metalinguistic knowledge of the target language. The tutee’s upshot formulation in particular also influenced the type of advice he received. Overall, this study highlights how peer tutees’ use of response formulations to advice, enhanced by the affordances of online mediation such as real-time audio interaction, facilitates greater conversational participation and deeper engagement, which leads to more meaningful, cooperative, and effective tutorials.