The ability to solve problems associated with the consequences of one's morals in general can be said to be vary according to the differences in personality, the way of thinking, and behavior. The difference in thinking skills of the students have prompted the authors to conduct a research to develop a moral dilemma worksheet in problems of forest ecosystem to train the students' critical thinking skills at SMP Negeri 6 Banjarmasin. This study used one group pretest-posttest design. The data of the research results showed that: (1) The developed worksheet, otherwise, was valid in overall by academician and practitioners, (2) The developed Worksheet has fulfilled the practical criteria based on the implementation of the lesson plan with good categories, (3) The worksheet is declared to be effective by achieving the score gain ie 0 , 66 with the medium category, and (4) Science process skills of students considered as good. Therefore, worksheet of moral dilemmas in problems of forest ecosystems were declared feasible (valid, practical, and effective) use to train students' critical thinking skills at SMP Negeri 6 Banjarmasin. Keywords : woksheet, dilemmad, problem, forest ecosystem