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 education at the Gymnasium in Brackwede-Bielefeld, Diekwisch pursued dental studies at the Philipps-University of Marburg in Hesse and graduated with a Doctorate in Dentistry (Dr. med. dent.) in 1988.