Humans need medicinal plants to continue their lives in a healthy way. This need will continue in the past, present, and future. The earth can be polluted naturally or by human sources. Medicinal plants consumed by humans for various purposes can be affected by this pollution. One of the important points that people should pay attention to is the use of medicinal plants without biological and chemical contamination. In this compiled book chapter, scientific studies on chemically and biologically contaminated medicinal plants and brain health are included. The current study is original and is expected to contribute to those interested in the subject.