The pre-test and post-test quasi-experimental design with control group was used in this study, in which the impact of alternative assessment activities on students' academic achievement levels and attitudes were explored by employing these activities in the unit "Electricity in Our Lives" of the Science and Technology Course. The research was carried out in three elementary schools in the city of Kocaeli, which exhibited three different levels of success in the SBS (National Level Determination Exam). The academic achievement test, which was one of the data collection tools of the study, was developed by the researchers and its reliability was found to be 0.85. A Likert-type scale, whose reliability was found to be 0.96, was employed in order to measure students' attitudes towards science. In addition, 14 alternative assessment activities were used in the study, which were developed by the researchers and composed of structural communication grid, diagnostic tree and predict-observe-explain activities. According to the findings of the research, a significant difference was found between the experimental and the control groups with respect to science attitudes and achievement in the favor of the experimental groups. A generally positive correlation was found between the mean scores that the students in the experimental group got from the activities and their achievement pre-test-post-test scores.