Purpose: Professional identity formation (PIF) is described as “a multifactorial phenomenon, shaped by ways that clinical and non-clinical experiences, expectations and environmental factors merge with individual values, beliefs and obligations.” 1 Data suggest that students’ personal characteristics factor in the PIF process. 2,3 This study examined how socioeconomic status (SES) (measured by generation college status [first-generation college graduate (FCG) vs continuing-generation college graduate (CCG)] and household income [high vs low]) might influence PIF among a national cohort of U.S. medical students. Method: We analyzed cohort data from an existing dataset of deidentified records from the Association of American Medical Colleges Graduation Questionnaire (GQ). 4 The GQ asks 2 questions related to PIF: (1) “My medical school has done a good job of fostering and nurturing my development as a future physician” and (2) “My medical school has done a good job of fostering and nurturing my development as a person.” We used GQ data from academic years 2014–2015 and 2015–2016. Multivariate regression models explored relationships between 4 categories of students’ SES with measures of PIF, controlling for covariates such as sex and race/ethnicity. CCG status was defined as having at least 1 parent/guardian with a bachelor’s degree. FCG status was defined as students with no parent with a bachelor’s degree. Household income was determined using 2 self-reported measures of income status: receipt of state or federal financial assistance, and parental income reported on the Matriculating Student Questionnaire. 5 Students were considered low-income if they indicated that their families were recipient of state/federal financial assistance programs (e.g., Supplemental Nutrition Assistance Program) or if their self-reported parental income was within the lowest 2 quintiles nationally (less than $41,187 for 2014–2015 cohort, and less than $43,512 for 2015–2016 cohort). A 4-level variable SES variable was created to reflect SES: continuing-generation college graduate/high income (CCG/HI), continuing-generation college graduate/low income (CCG/LI), first-generation college graduate/high income (FCG/HI), and first-generation college graduate/low income (FCG/LI). Statistical analyses were performed using STATA16.1. Results: Of the 24,796 students in our sample, 64.4%, 20.9%, 4.2%, and 10.5% identified as CCG/HI, CCG/LI, FCG/HI, and FCG/LI, respectively. CCG/LI respondents were less likely than CCG/HI peers to report that their medical school had done a good job of fostering and nurturing their development as a person (aOR: .79, 95% CI: .74, .85) and that their medical school had done a good job of fostering and nurturing their development as a future physician (aOR: .71, 95% CI: .63, .80). Similarly, FCG/LI respondents were less likely than FCG/HI peers to report that their medical school had done a good job of fostering and nurturing their development as a person (aOR: .85, 95% CI: .78, .94) and that their medical school had done a good job of fostering and nurturing their development as a future physician (aOR: .72, 95% CI: .62, .84). No significant differences were observed between FCG/HI and CCG/HI respondents on either aspect of PIF. Discussion: Our study illuminates nuances in PIF and provides new knowledge that, regardless of college graduate generation status, students who self-identified as being from low-income backgrounds were less likely than their high-income peers to report that their medical schools were doing a good job fostering personal and professional identity formation. Significance: These results reinforce that understanding the PIF experiences of diverse groups of medical trainees is critical to advance equity. More attention must be paid to the experiences of low-income students to ensure that they are and feel supported in their professional development and leave medical school equipped to thrive in their subsequent careers.