This study aimed to understand the medical sciences students' critical thinking (CT) and their learning styles and investigate the relationship between academic performance and the both mentioned variables. A descriptive analytical study was conducted on 469 medical sciences students in Ardabil University of Medical Sciences using the Kolb's learning styles and California's CT skills test (Form-B). Cumulative grade point average was considered as academic performance. The data were analyzed with SPSS 18 and using Chi Square test, Independent t-test, one-way ANOVA and Pearson correlation test with a significant level of p < 0.05. The mean of academic performance was 15.9 ± 1.7. The popular learning style among students was assimilative style. Results showed significant relationship between academic performance and learning style. Significant relationship between academic performances of students with the total CT skills was not found, but significant relationship was seen between academic performance and deductive skill only. Learning styles changed in different semesters among medicine and dentistry students from an abstract-reflexive style to a concrete-active one. Using appropriate, active and collaborative teaching methods can help to improve learning and students' academic performance.