Background The lack of clinical competence in nurses leads to problems in providing nursing services. Studies indicate that nurses lacking the required skills can endanger the public health in medical centers. Critical thinking is a factor that can affect nurses' clinical competence. Objectives The current study aimed at investigating the relationship between critical thinking and clinical competence in nurses. Methods The current descriptive-analytical and cross sectional study was conducted on 120 nurses selected by random sampling method. Data collection tools included the California Critical Thinking Disposition Inventory (CCTDI), as well as clinical competence and demographic information questionnaires. Data were analyzed with SPSS using Pearson correlation coefficient, linear regression, and -test. Results Pearson correlation test showed a positive correlation between the total scores of critical thinking and clinical competence. Based on the results of the linear regression analysis, the tendency toward critical thinking could predict 28.4% of the clinical competence. The nurses mean CCTDI scores were at the positive level and their mean clinical competence scores were at the average level. Conclusions According to the obtained results, nursing authorities can organize practical workshops on the development of critical thinking of clinical nurses as one of the most important and operational strategies to improve nursing clinical competence and, ultimately, move towards optimal care.