This research aims to develop the environmental recreation camp activity for youth in Roi-Et province of Thailand, to compare environmental knowledge, environmental attitudes before and after participating in the camp, as will as their participating in Environment Recreation camp activities during and after participating in the camp of youths with different gender and domicile, and to study the relationship between environmental knowledge, environmental attitudes and participation in environmental recreation camp activities. The data were collected though a survey with 40 youths from Phanom Phrai Wittayakarn School, Phanom Phrai District, Roi-Et Province. The research instruments was the manuals questionnaire measuring environmental knowledge, environmental attitudes and participation in environmental recreation camp activity. The data were analysed by using descriptive statistic and hypothesis testing by using t-test, One-way MANCOVA, One-way ANOVA and Correlation analysis. The results of this research indicated as below Environment Recreation Camp Activities for Youth in Roi-Et Province had effectively is 85.17/83.44 and an effectiveness index is 0.6117. After participating in environment recreation camp activities, youths had higher environmental knowledge and environmental attitudes than before participating in the camp. After participating in environment recreation camp activities, youth had higher participation in environment recreation camp activities than during participating in camp. The sample youths with different gender and domicile had no different environmental knowledge, environmental attitudes, and environmental participation. Environmental knowledge, environmental attitudes, and participation in environmental recreation camp activities were not correlated.