The purposes of this research were to develop learning plans for dam management in the Northeast of Thailand using case study-based learning being efficient and effective, to study and compare the knowledge, attitude, and environmental ethics concerning dam management in the Northeast of Thailand before and after learning, and different gender. The sample was 72 2nd-year students in Environmental Education program, Faculty of Environment and Resources Studies, Mahasarakham University, being selected by purposive sampling. Research tools were learning plans for dam management in the Northeast of Thailand, knowledge test, attitude test and an environmental ethics test. The statistics used in the research were frequency, percentage, mean, standard deviation, Paired t-test, and One-way ANOVA. The results of the research were found that: 1) The efficiency of learning plans was equal to 86.38/84.17, and the effectiveness index of learning plans was 0.7466. It showed that the students increased knowledge and resulted in the students progressing from their studies as 74.66 percent. 2) After the learning, the mean score of knowledge, environmental attitude, and environmental ethics of students were significantly higher than before the learning at the .05. 3) There was no different knowledge, environmental attitude, and environmental ethics between students with an different gender.