This study was aimed to examine guided inquiry-based learning effect, which is in the "human body systems" unit at the seventh-grade level, on academic achievement and scientific process skills. In this direction, the study was conducted with 46 seventh-grade students. One of the groups consisting of 23 students constituted the experimental group where the guided inquiry practices designed by the researchers were performed. And the other group constituted the control group where learning was provided through the direct instruction method. Data were obtained by the scientific process skills test and academic achievement test. These tests applied before and after the lessons to both groups. When the data were analyzed, the academic achievement test mean score of the experimental group was higher if we compare with the control group. But the mean score was not statistically significant. In the mean scores of the scientific process skills test, it was concluded that there was a statistically significant difference in favor of the experimental group. Accordingly, it is thought that guided inquiry-based learning can contribute the basic scientific process skills of the students but there is no extra contribution found to academic achievement if the concepts are easy to remember.