The United States has been a top destination country for science and engineering (S&E) graduate education for foreign talent for many years. Despite the clear existence of foreign students in the USA, relatively little is known about the factors influencing the flow of foreign students. In this study, we examine foreign doctoral students in science and engineering, and test whether “ethnic affinity” plays a role in the ethnic composition of research laboratories (in what follows, “labs”) in US universities. In order to test this hypothesis, we conduct a web search, and select 164 science and engineering laboratory web pages for analysis. Among these 164 labs, 82 are directed by foreign-born faculty (Korean, Chinese, Indian or Turkish). These 82 are matched with labs that are in the same department of the same university, but directed by a native (US origin) faculty member. We find strong evidence that labs directed by foreign-born faculty are more likely to be populated by students from the same country of origin than are labs directed by native faculty. The percentage of students working in a lab from a nationality (foreign or native) is higher when they share nativity with the director. We seek to draw attention to the effect of affinity on the ethnic composition of research labs at the micro level that translates into the ethnic composition of the scientific community at the macro level. Further, these results emphasize the role of lab directors in future enrolments, creating scientific human capital, and contributing to the “brain circulation” phenomenon in the global context.