In cell therapy, the use of autologous and allogenic human mesenchymal stem cells is rising. Accordingly, the supply of cells for clinical applications in highest quality is required. As hMSCs are considered as an advanced therapy medicinal products (ATMP), they underlie the requirements of GMP and PAT according to the authorities (FDA and EMA). The production process of these cells must therefore be documented according to GMP, which is usually performed via a GMP protocol based on standard operating procedures. This chapter provides an example of such a GMP protocol for hMSC, here a genetically modified allogenic cell line, based on a production process in a microcarrier-based stirred tank reactor including process monitoring according to PAT and final product quality assurance.