In this study, students' views on the process of authentic assessment and implementation of a unit which was designed by using conceptbased interdisciplinary approach were examined. To achieve this, the influence of implementation on teaching-learning process and also students' perceptions about authentic assessment were investigated. The study was conducted as a case study which is one of the qualitative research designs. The sampling group was composed of 14 students. Data collected through interviews, observations and journals were analyzed with the help of content analysis method. Results indicate that students thought that the implemented activities were different from the previous ones. These activities made students' interest into lessons to increase and contributed to developing positive attitude and working collaboratively. Students also thought that authentic assessment activities were different from previous ones in terms of being oriented to learning process, being student-centered, requiring metacognitive strategies and usage of information about various disciplines. Interdisciplinary activities and the process of authentic assessment prepared by teachers consciously provided beneficial contributions for students to take responsibility of their learning and for teachers to make more realistic assessment. For this reason, it is useful for teachers to develop their skills in designing interdisciplinary programs and authentic assessment.