This study aimed to investigate the usefulness of a newly developed oral simulator for nursing students' oral assessment education on oral diseases and symptoms. The participants were first-year students (n=105) at a nursing school in Japan. Ten identical oral simulators with angular cheilitis, missing teeth, dental caries, calculus, periodontitis, hypoglossal induration, food debris, and crust formation were created by a team of dentists. After a 45-minute lecture programme for oral assessment performance with the Oral Health Assessment Tool (OHAT), the ability test with the simulators and the OHAT as well as test feedback were conducted in a 30-minute practical programme. To evaluate the effectiveness of the programmes, questionnaires and ability tests with slides of oral images were conducted at baseline and after the programme. Ninety-nine students (94.3%) participated in this study. The results of the ability test with the simulators and the OHAT in the practical programme showed that the correct answer rates of assessing tongue, gingiva, present teeth, and oral pain were less than 40%. Their levels of confidence, perception, and oral assessment performance were statistically significantly higher after the programmes than they were at baseline. Their level of confidence in assessing the need for dental referral had the largest increase in scores compared to the lowest scores at baseline in the nine post-programme assessment categories. This study identified several problems with nursing students' oral assessment skills and improvements of their oral assessment confidence, perceptions and performance.