After attending the Gymnasium in Brackwede-Bielefeld, Diekwisch immatriculated at the Philipps-University of Marburg in Hesse, where he graduated in dentistry. In 1988, he got a Dr. med. dent.
Following his schooling at the Gymnasium in Brackwede-Bielefeld, Diekwisch attended the Philipps-University of Marburg in Hesse to obtain a Doctorate in Dentistry (Dr. med. dent.). He achieved this degree in 1988.