Background: Depression is a worldwide public health problem that requires the attention of qualified health professionals. The training of skilled nurses is a challenge for nursing instructors due to the complexity of this pathology. Objectives: The aim was to analyse the declarative and argumentative knowledge acquired about depression by students receiving traditional expository instruction versus students receiving problem-based learning instruction. Methods: Quasi-experimental study with pre-test and post-test design in experimental and control group to measure differences in the improvement of declarative and argumentative knowledge. Non parametric tests were used to compare the scores between the experimental group and the control group, and between the pre-test and post-test in each group. 114 students participated in the study. Implementation of the study took place during the 2014-2015 academic year in the third year of the Nursing undergraduate degree courses in the University of the Basque Country (UPV/EHU) as part of the Mental Health Nursing subject. Results: The data indicated that there were no statistically significant differences between the two methodologies in regard to declarative knowledge in the care of patients with depression. Nevertheless, the argumentative capacity of the experimental group improved significantly with the problem-based learning methodology (p = 0.000). Conclusions: The results of the implementation indicated that problem-based learning was a satisfactory tool for the acquisition of argumentative capacity in depression nursing care. Still, working examples of teaching sequences that bridge the gap between general clinical practice and classroom practice remain an important goal for continuing research in nursing education. (C) 2017 Elsevier Ltd. All rights reserved.