The Botanic Garden of Johannes Gutenberg University Mainz has five main purposes:

Research and teaching: This is the main function of the Mainz garden, which is affiliated with the Institute of Special Botany of the Faculty of Biology. The garden supports on-going research projects of work groups through the provision of experimental test areas and research materials. Special collections are built temporarily for individual projects. The garden delivers conceptual material for the courses and cultivates a broad spectrum of endogenous plants for identification in basic studies courses. Students thus have the opportunity to get to know the various plants directly.

Continuing education and public relations: A wide audience is made aware of the Botanic Garden through presentations of its collections, public tours, exhibitions, brochures, and information boards. It offers an opportunity to all who may be interested, to school classes, clubs, and private groups to comprehensively inform themselves about botanical topics. Building awareness of the significance of plant diversity is one of the garden's central concerns.

Conservation of biological diversity: The Mainz Botanic Garden endeavors to cultivate plants threatened by extinction in Rhineland-Palatinate. At the center of interest is the vegetation of the nature reserve "Mainzer Sand," which will be preserved in the Botanic Garden in a close reproduction of the natural habitat ("ex-situ"). The garden also contributes towards the measures used to maintain the "Mainzer Sand" nature reserve.

Horticultural training program (ornamental plants): Horticultural knowledge and know-how are indispensable for the presentation and preservation of plant diversity. It is for this reason that its horticultural training program is so important to the Botanic Garden. There are currently nine training places available. In contrast with market gardens, where only a few plant varieties are grown, future gardeners are made familiar with the conditions for the cultivation of a broad spectrum of different plants.

Culture and recreation: Aside from its role in research, teaching continuing education, and species protection, the Botanic Garden provides a venue for interdisciplinary discussion and relaxation on the campus of Johannes Gutenberg University. Through events such as the "Summer Fest," "Tropical Night," and "Music in the Garden," it attracts thousands of visitors annually and acts as an important link between the university and the population in the region.