This study examined the effects of inquiry-based biology laboratory applications on pre-service biology teachers' scientific process skills, attitudes, self-efficacy, and self-confidence in the laboratory. In this context, many related tests and scales were applied to first-year students of biology education (N=25). The research adopted the pretest and post-test control group model. The results showed that laboratory practices based on both the corroborative and the guided inquiry approach increase the scientific process skills of the prospective teachers. Guided inquiry-based laboratory practices have increased the attitudes of pre-service biology teachers toward laboratory lessons. However, self-efficacy and self-confidence of the pre-service teachers taking part in corroborative laboratory practices increased, while guided inquiry methods did not have a significant effect on self-efficacy and self-confidence. The findings of the study highlighted the importance of a guided inquiry approach in the laboratory applications related training of pre-service biology teachers.