Contribution: This paper explores the factors contributing to the development of engineering identity in Latinx students at two institutions. A better understanding of these factors will support the development of more inclusive engineering education environments and experiences. Background: Persistence of Latinx engineering students is of particular interest due to their underrepresentation in the field. Identity is a lens for understanding student persistence, but Latinx students are underrepresented in prior engineering identity studies. This paper seeks to identify the unique factors, academic and professional, that contribute to engineering identity development, and potential means for supporting the persistence of Latinx engineers. Research Questions: 1) What academic and professional affect factors predict engineering identity development of Latinx students? and 2) What role does the institution play in Latinx students' engineering identity development? Methodology: A mixed-methods approach was used to measure engineering identity based on a framework incorporating both academic and professional affect elements. Regression analyses were conducted on 892 responses to an online survey from Latinx engineering students, with additional insight from interviews with ten Latinx engineering students. Findings: Six of the nine factors analyzed (performance/competence, interest, recognition, analysis, framing and solving problems, and tinkering) were significant predictors of Latinx students' engineering identity, as were institution, gender, and having a parent with an engineering degree. Engineering identity was higher for Latinx students at the Hispanic Serving Institution, but none of the interaction terms were significant, so the relationship between these factors and engineering identity is similar at each institution.