<p>Branch campuses have become a global phenomenon in higher education. This study investigates whether the establishment of elite cross-city branch campuses enhances or crowds out the scientific research performance of incumbent local universities in China. Leveraging the staggered entry of 44 elite branch campuses across 26 cities as a natural experiment, we employ a staggered difference-in-differences (DID) and a triple-difference (DDD) design using a comprehensive panel dataset from 1994 to 2020. Our results show that the establishment of cross-city branch campuses significantly increases scientific research output of local universities, with a 12.9% increase in the total number of publications. Event-study estimates further indicate that the effect develops gradually after branch-campus entry. Mechanism analysis points to an important role of increased inter-institutional research collaboration with the entrant universities. The positive effects are more pronounced when the incoming branch campus belongs to a top-tier elite university (Project 985). This paper provides robust causal evidence informing the strategic spatial allocation of higher education resources and regional innovation policies.</p>