The present study aimed at investigating the effect of using a project based learning strategy on the development of the environmental concepts and the attitude towards the environment among grade four The sample of the study consisted of (48) students of grade_4 in one of Al.Dhakiliya schools. Students were distributed into two groups: An experimental group consisting of (24) students. This group studied the unit of "the natural habitat" in the science book, through a guide book designed by the researcher. The students were required to apply twelve environmental concepts in eight projects. The concepts are: natural habitat, the group, biological society, aquarium, adaptation, camouflage, distinction, fossils, pollution, natural changes, artificial changes and reservations A control group, consisting of (24) students, studied the same unit with the traditional method. The two groups studied the unit two month during the second semester of the school year 2013/2014. To answer the study questions, the researcher designed two instruments. The first one was a test on environmental concepts. It consinted of (24) multiple-choice questions on 12 environmental concepts. The validity was found by agroup of judjements and the reliability of the test was checked through testing and re-testing. Pearson correlation was (0.85 )The second instrument was The Attitude towards the Environment scale consisted of 15 items distributed in three sections: maintaining the environmental cleanliness, reserving the environmental resources, and protecting the Omani environment. The validity was found by agroup of judjements. The reliability of the scale was checked through alpha cronbach which was (0.85) The study found that there were statistically differences at (o= 0.05) between the means of the two groups in both instruments for the benefit of the experimental group. The study recommends training students an accomplish projecy about the environmental issues, and encouraging science supervisors and teachers to participate in designing educational, national projects which can be presented in international conferences such as Global Summit Conference.