Teacher working conditions (TWCs) are, in many ways, student learning conditions. Furthermore, they have also been linked to teacher retention. These connections make TWCs important to understand; yet there is no accepted construct definition delineating and defining what TWCs are. Through a systematic review and narrative synthesis of literature from the United States, I define TWCs and organize the topics that emerged from the literature into a catalog of TWCs. After defining what TWCs are, I employ findings from the narrative synthesis to discuss what TWCs are not. Additionally, I document sources of variation in operationalizing TWCs as well as areas of homogeneity in how researchers study TWCs. I find that researchers agree on the underlying concept of TWCs, vary widely in how they decompose the concept, and overwhelmingly use survey methods to study TWCs. Last, I offer three suggestions to consider in future research.