This case-control study aimed to verify the effects of oral health education in terms of the changes between Patient hygiene performance index (PHP-M) and dental health knowledge and the planned behavior theory variables in inpatients alcoholics. A total of 32 patients at education group and 30 at non-education control group were recruited. The minimum score of PHP-M becomes 0, and the maximum score is 5. Theory of Planned Behavior (TPB) was composed of 5 articles, and was measured in the 5-point rating scale. Oral health education program was published by the Korean Dental Health Association. Dental health knowledge was presented in 10 questionnaires on a maximum of 10 points, by self-administered questionnaire systems. Independent-sample t tests, Repeated-sample t tests, Pearson’s chi-square tests were applied for statistical analysis. The dental health education for alcoholics patients had effects on dental health behavior, PHP-M and dental health knowledge. Dental health behavior had an influence on behavior intention and perceived behavior control among planned behavior variables, and its influence was getting bigger through dental health education. Therefore it is necessary to try to develop and apply the dental health education program which can promote dental health through dental health education for subjects whose dental environments are poor and who have lower oral management ability.