Background: Young people increasingly turn to the Internet for information about social and political issues. However, they struggle to evaluate the trustworthiness of the information they encounter online. Aims: This pilot study investigated whether a focused curricular intervention could improve university students' ability to make sound judgements of credibility. Sample: Participants (n = 67) were students in four sections of a 'critical thinking and writing' course at a university on the West Coast of the United States. Course sections were randomly assigned to treatment (n = 29) and control conditions (n = 38). Methods: We conducted a pre-and-posttest, treatment/control experiment using a 2 × 2 × 2 design (treatment condition × order × time) with repeated measures on the last factor. Students in the treatment group received two 75-min lessons on evaluating the credibility of online content. An assessment of online reasoning was administered to students 6 weeks prior to the intervention and again 5 weeks after. Results: Students in the treatment group were significantly more likely than students in the control group to have shown gains from pretest to posttest. Conclusions: Results suggest that teaching students a small number of flexible heuristics that can be applied across digital contexts can improve their evaluation of online sources.