Letters of recommendation (LORs) are a significant component of the residency application process. [1][2][3] Historically, standardized exams, clerkship grades, and honor societies, were prioritized. 4 However, the shift to holistic review, combined with pass/fail scoring for United States Medical Licensing Examination (USMLE) Step 1, has diminished the rigid, metric-driven components of the application. 5,6 LORs increasingly factor into the decision making process for interview invitations and rank lists. 7 Further, studies have shown LORs to be often biased against women and applicants underrepresented in medicine (UiM). 8 While there is guidance on writing standardized LORs, resources for creating a narrative LOR are more limited. 2,[9][10][11][12][13][14][15] This primer will guide authors on writing narrative LORs for medical students who are applying to residency programs.Recommendations are based on published evidence and the combined experience of the authors. All authors have held positions as advisors and mentors to medical students, residents, fellows, and faculty across four separate academic institutions (e.g., core residency faculty, leadership in undergraduate and graduate medical education, service on medical school admissions committees, residency and fellowship selection committees, and authorship of numerous LORs across all levels of training).