Background: Academic achievement is one of the most important indicators in evaluating education. Various factors are known to affect the academic achievement of students. Purpose: This study was performed to assess the relationship between critical thinking skills and learning styles and the academic achievement of nursing students. Methods: In this cross-sectional study, 139 sophomores to senior year nursing students were selected using a simple random sampling method. The data were gathered using a three-part questionnaire that included a demographic questionnaire, the Kolb's Learning Style Standard Questionnaire, and the California Critical Thinking Skills Questionnaire. The previous semester's grade point average of the students was considered as a measure of academic achievement. The data were analyzed using descriptive and analytical statistics in SPSS 20. Results: The mean score for critical thinking skills was 6.75 2.16, and the highest and lowest scores among the critical thinking subscales related to the evaluation and analysis subscales, respectively. No relationship between critical thinking and academic achievement was identified. “Diverging” was the most common learning style. The highest mean level of academic achievement was earned by those students who adopted the “accommodating” style of learning. Asignificant relationship was found between learning style and academic achievement (p < .001). Conclusions: According to the findings, the critical thinking skills score of students was unacceptably low. Therefore, it is essential to pay more attention to improving critical thinking in academic lesson planning. As a significant relationship was found between learning style and academic achievement, it is suggested that instructors consider the dominant style of each class in lesson planning and use proper teaching methods that take into consideration the dominant style.