Objective: The aim of this study was to compare the effectiveness of cooperative learning and traditional learning methods on the development of drug-calculation skills. Design: Final-year nursing students ("n" = 85) undergoing internships during the 2010-2011 academic year at a nursing school constituted the study group of this quasi-experimental study. Setting: Students were divided into two groups: an experimental group and a control group. A cooperative learning method was introduced to the experimental group ("n" = 32) and a traditional learning method was applied to the control group ("n" = 40). Pre-test and post-test scores of drug-dose calculation skills were compared. Method: Data were obtained using data collection forms which were developed by the researchers. Statistical analysis was performed using the Statistical Package for the Social Sciences for Windows version 15.0. "T"-test and Wilcoxon's signed rank test with Bonferroni correction were used for comparison of drug-dose calculation skill scores between groups and within groups before and after training. Results: No statistically significant difference was found between drug-dose calculation pre-test scores of both groups ("p" = 0.144). After training, while the post-test mean score of the control group was 92.00 ± 7.90, this score was 87.03 ± 9.98 in the experimental group and the difference was statistically significant ("p" < 0.05). Conclusion: After training, drug-dose calculation skills of students were increased in both groups. But the traditional learning method was found to be more effective than the cooperative learning method in the development of drug-dose calculation skills.