The aim of this research is to examine the effects of laboratory activities based on the predict-observe-explain (POE) strategy on the understanding of photosynthesis and respiration concepts of pre-service science teachers, and their attitudes towards biology science and course and biology laboratory. Pre- and post-test designs with an experimental and a control group were used in the research. The research was implemented with participation of 64 the pre-service science teachers. For this purpose, the experimental and the control groups were randomly determined. The same laboratory activities were carried out using POE in the experimental group and utilising a traditional approach in the control group. For the data collection, a two-tier concept test, The Biology as a Science and Course Attitude Scale and the Biology Laboratory Attitude Scale were applied before and after the applications. The results indicated that the pre-service science teachers who were taught using laboratory activities based on the POE strategy had significantly higher scores in terms of achievement and attitude towards biology laboratory than those taught by the traditional approach. In this context, we recommend using and expanding laboratory activities based on active learning methods, such as POE in biology courses.