Written Corrective Feedback (WCF) is a common formative feedback strategy in the language classroom, yet it is unclear whether it is effective and in which contexts. This study aims to determine the influence of learner proficiency in the effectiveness of two different types of WCF and whether learner proficiency influences how learners respond to two different types of WCF. Using an embedded, mixed methods design, seven participants wrote three writing samples and receiving two different types of feedback. Following the writing samples, the participants were asked to think aloud as they reviewed the feedback for the first time, followed at the end by retrospective, semi-structured interviews. The findings suggest that learner proficiency did not influence the effectiveness of the two different types of WCF, however they did reveal that learners at both the beginner and advanced levels lack effective strategies for responding to feedback.