Background: Grade inflation in higher education institutions, that is the increase in students’ grades, has been observed since the 1960s. There are comprehensive proofs that document the allegations, prevalence and severity of grade inflation in higher education especially in American universities for the past 10 years. This study analyzes the change in the ratio of those graduated with a “very good (>2.99)” degree from medical education in Turkey within a 15-year-long period, the grade inflation (when all other factors are constant), and factors that affect the course grade. Methods: The analyses were carried out using the grade point average (GPA) of 9.618 students graduated from the medical faculty of 25 universities in Turkey, and 288.540 student grade for 7.597 courses. The study used the “real” university random effects estimator modeling considering the differences in universities with correlation, ANOVA, t-test and ANCOVA analyses. Results and Conclusion: The results revealed that there was a marginal increase in grades in medical training before graduation after checking the effects of factors that might affect the graduation grades. The 29% grade inflation detected is in line with the literature and is one of the highest values that have been reported so far. It was also detected that the ratio of graduates with a “very good (>2.99)” degree was 17% in 2005 and it increased to 46% in 2020. Additionally, the class size, academic degree of the tutor, grade, content of the course, types of the universities (public & non-profit private), accreditation of the program, and the age of the faculty are important determinants of course grades. According to these results, it is clear that both the uncontrolled expansion of medical faculties in Turkey and the decrease in quality cause an increase in grades. One of the most important results obtained is that accreditation slows down the grade inflation. Both the course grades following the accreditation process and the inflation in the graduation grades (grade inflation) slowed down significantly in the accredited faculties. This finding is an important example of the necessity of accreditation, which is referred to as the “golden standard” to improve the quality of medical education.