Context: Ethnicity-related differences in clinical grades exist. Broad sampling in assessment of clinical competencies involves multiple assessments used by multiple assessors across multiple moments. Broad sampling in assessment potentially reduces irrelevant variances and may therefore mitigate ethnic disparities in clinical grades. Objectives: Research question 1 (RQ1): to assess whether the relationship between students’ ethnicity and clinical grades is weaker in a broadly sampled versus a global assessment. Research question 2 (RQ2): to assess whether larger ethnicity-related differences in grades occur when supervisors are given the opportunity to deviate from the broadly sampled assessment score. Methods: Students’ ethnicity was classified as Turkish/Moroccan/African, Surinamese/Antillean, Asian, Western, and native Dutch. RQ1: 1667 students (74.3% native Dutch students) were included, who entered medical school between 2002 and 2004 (global assessment, 818 students) and between 2008 and 2010 (broadly sampled assessment, 849 students). The main outcome measure was whether or not students received ≥3 times a grade of 8 or higher on a scale from 1 to 10 in five clerkships. RQ2: 849 students (72.4% native Dutch students) were included, who were assessed by broad sampling. The main outcome measure was the number of grade points by which supervisors had deviated from broadly sampled scores. Both analyses were adjusted for gender, age, (im)migration status and average bachelor grade. Results: Research question 1: ethnicity-related differences in clinical grades were smaller in broadly sampled than in global assessment, and this was also seen after adjustments. More specifically, native Dutch students had reduced probabilities (0.87–0.65) in broadly sampled as compared with global assessment, whereas Surinamese (0.03–0.51) and Asian students (0.21–0.30) had increased probabilities of having ≥3 times a grade of 8 or higher in five clerkships. Research question 2: when supervisors were allowed to deviate from original grades, ethnicity-related differences in clinical grades were reintroduced. Conclusions: Broadly sampled assessment reduces ethnicity-related differences in grades.