A number of benefits of environment based learning have encouraged the authors to conduct the research which was intended to develope instructional materials based on Barito riverbank environment to train the students’ science process skill in SMA Negeri 1 Marabahan. This research used one group pretest-posttest design. The data of research results showed that: (1) the developed of instructional materials were declared valid according to practitioner and academician judgment with good category on the whole (2) the developed of instructional materials fulfilled the practical criteria based on the application of the lesson plan with good category, (3) Furthermore, the developed instructional materials were also declared effective based on the gain score attained, 0.67 with medium category, and (4) students’ science process skill was categorized as good. Therefore, the instructional materials based on Barito riverbank were declared feasible (valid, effective, and practical) to be used to train students’ science process skill in SMA Negeri 1 Marabahan. Keywords: instructional materials, environment learning based, riverbank, science process skill.