This study aims at determining the science concepts and subjects used in the "religion courses" taught in secondary schools and the contribution of science to religion courses, which is not a widely studied topic in the relevant literature. Like qualitative research, this study is a multiple case study. The data were collected using a semi-structured interview with five Muslim religion teachers working in an eastern city of Turkey. The interview data were analyzed using the basic descriptive and content analysis methods. The findings showed that religion teachers benefit from the concepts and subjects of science in their courses; using life sciences in their religion courses had a positive impact in teaching religious subjects better to the students; the use of the concepts of life sciences in religion courses enabled students to perceive the subject better; students enjoyed the use of science concepts in religion courses and also students asked questions to their teachers about many subjects of life sciences. Religion teachers expressed that they did not feel competent enough in the life sciences. Some recommendations, such as organizing in-service training have been made for religion teachers to feel competent enough in life sciences.