The purpose of this study is to investigate the effects of the conceptual change text based instruction on ninth grade students' understanding of ecological concepts, and attitudes toward biology and environment. Participants were 82 ninth grade students in a public high school in the Northwestern Turkey. A treatment was employed over a five-week period with quasi-experimental design. While two classes were called control group, two classes were called experimental group. Each teacher had one control group and one experimental group. Two teaching methods were used and randomly assigned to one class of each teacher. While the control group received traditional instruction, the experimental group received conceptual change texts based instruction. Ecology Concepts Test, Attitude Scale towards Biology and Attitude Scale towards Environment were administered to the participants as pre- and post-tests. Data of interview and observation were also collected to support the study results. The results showed that the effect of the conceptual change texts based instruction was better than the traditional instruction on understanding of ecological concepts. However, there was no statistically significant effect of the treatment on the participants' attitudes toward biology and environment.