Understanding resonance is essential to predict chemical reactivity and explain reaction mechanisms. Despite its importance in the organic curriculum, few studies have explored students' difficulties with this concept and faculty's instructional approaches to teaching it. The goals of this study are to address this gap in the literature by (1) employing an exploratory mixed-methods design to characterize students' conceptual struggles with resonance and (2) exploring the relationship between students' struggles and the instructional approach employed. Leveraging the results of a set of interviews with organic chemistry students, we distributed a survey to students in two different sections of a first-semester organic chemistry course at a research-intensive institution. We also conducted postinstruction interviews with the two instructors of the surveyed sections. Analysis of the 180 surveys collected indicates that students tended to focus on the features and processes of recognizing and drawing resonance structures when asked to explain the concept of resonance and mostly did not understand the relationship between resonance structures and the resonance hybrid. A comparison of the two sections showed a significant difference with one section having a better conceptual understanding of resonance than the other. Analysis of the instructional approaches demonstrated that the instructor of the section with higher conceptual understanding focused his instruction on the limitations of chemical representations, while the other instructor focused on the features and processes of recognizing and drawing resonance. This study highlights the need to help students develop metarepresentational competence as well as to better understand instructors' instructional decisions.