INTRODUCTION. Critical thinking is vital in both science and daily life, being crucial for identifying anecdotal evidence, unfalsifiable hypotheses, biased data sampling, and unreliable causal connections. This study aimed to adapt Lawson’s revised version of the Psychological Critical Thinking Exam (PCTE) into Spanish, and to use it to assess improvement in Psychology students taking a module on reasoning. METHOD. Eighty-seven third-year Psychology students responded to the odd items of the original PCTE at the beginning of the term, and to the even items at the end. During the module, one session was dedicated to discussing Lawson’s critical thinking questions, evaluating the reliability of purportedly scientific statements. RESULTS. Students’ critical thinking skills improved both in problem detection (i.e., volunteers who initially failed to identify methodological problems, then did) and in accurately detecting the target problem (i.e., issues related to the critical thinking question addressed). DISCUSSION. We consider the PCTE a valuable tool for assessing and developing critical thinking among university students. Moreover, we suggest that this study itself could serve as didactic material for analysis by students, enhancing their critical thinking skills.