Research has indicated that, in comparison to their counterparts at predominantly White institutions (PWIs), Latinx students at Hispanic-Serving institutions (HSIs) tend to encounter less racism and, in turn, fewer challenges in shaping their ethnic identity development. Yet, evidence has also suggested that the disciplines, and by extension, the departments in which Latinx at HSIs are enrolled (e.g., STEM vs. non-STEM) affect how they encounter racism. To further explore the ecological influence of the discipline and department on Latinx identity development in HSIs, we examined Latinx student experiences in one of the least diverse STEM disciplines, computer science. We analyzed interview and observation data from a multi-case ethnographic study of computer science departments at three HSIs to examine students' experiences as they navigated their majors. We found that these students experienced challenges similar to those of students at other institutions, such as a lack of academic preparation, limited self-confidence, and scarcity of Latinx representation, which hindered their sense of belonging. Yet, these students also encountered developmental support through student-initiated and department-initiated efforts, which encouraged them to engage in leadership and professional development opportunities. These findings suggest that STEM academic departments at HSIs can play a critical role in the development of Latinx students' ethnic identity.