Existing scholarship finds that having an attorney in immigration legal proceedings increases the chances of a favorable outcome. This work, however, often acknowledges that the representation effect is underexplained: selection may explain outcomes, and variation among attorneys is difficult to assess. Through 103 interviews with attorneys who practice immigration law in three organizational environments (nonprofit legal services, private firms, and corporate law firm pro bono programs) in two East Coast areas, this paper argues that attorneys' sorting of clients between different types of legal organizations helps explain the representation effect. Attorneys define what type of case is a “good fit” for their representation, selecting cases they think they can help increase the probability of a favorable outcome. However, what they define as a “good fit” varies by attorneys' practice environments, and centers not only on the facts or characteristics of a client and their case, but also attorneys' organizational constraints. By documenting the central role of practice environment variation and its organizational constraints on attorneys' case selection, this paper helps explain the representation effect and its implications for increasing vulnerable immigrants' access to legal representation in the United States.