The objective of the study was to determine the effect of the Konstanz method of moral dilemma discussion (KMDD) on moral judgment in allied health students. The study employed the Moral Judgment Test, translated from English into Thai and validated in 247 students, as an moral judgment instrument. The scale satisfied four validity criteria: preference hierarchy, quasi-simplex structure of stage preference, affective-cognitive parallelism, and positive correlation between education and moral competence score (C-index). Test-retest reliability at a 1-month interval was 0.90. To investigate the impact of the KMDD, 83 pharmacy technician and dental nursing students were asked to participate in the study. The subjects were randomly assigned into control (n = 41) or experimental (n = 42) groups. The experimental group participated in a 90-min KMDD once a week for 6 consecutive weeks. Students in the control group also met once a week for 6 weeks to discuss the topics not related to ethics. All subjects completed the Moral Judgment Test before and after the intervention and again 6 months later. Split-plot ANOVA of the C-indexes at the beginning revealed that the experimental and control groups were not different (20.57 +/- 13.45 and 24.98 +/- 16.12). However, the experimental group scored significantly higher than the control group did after the intervention (35.18 +/- 10.96 and 24.20 +/- 14.70) and 6 months later (33.00 +/- 11.02 and 23.67 +/- 14.35). The KMDD appears to be a practical and effective intervention for developing moral judgment in allied health students. The effect on moral judgment remains at least 6 months after the intervention.