Objective To evaluate the effectiveness of scenario-based scaffolding instruction in teaching Comprehensive Geriatric Assessment (CGA) to undergraduate nursing students. Methods Two cohorts of undergraduate students majoring in Gerontological Nursing-the Class of 2021 (n=38) and the Class of 2022 (n=33) were assigned to the control group and the intervention group, respectively. The control group received conventional blended online-to-offline teaching combined with clinical practicum, while the intervention group, in addition to the conventional methods, participated in scenario-based scaffolding instruction. Both groups were compared in terms of written and CGA hands-on examination scores, as well as overall CGA competence assessed using a questionnaire. Results Students in the intervention group achieved significantly higher scores in both written and CGA hands-on examinations, as well as in the overall CGA competence and its knowledge, attitude, and practice domains (all P<0.05), compared to the control group. Conclusion The integration of scenario-based scaffolding instruction into CGA teaching enhances undergraduate nursing students′ understanding and application of geriatric assessment knowledge, thereby improving their overall assessment competence.