Hans Greger started practising judo in 1963 and ju-jutsu in 1967. He graduated to 1st Dan in ju-jutsu in July 1970 and received 10th Dan at Easter Camp in 2008. He also trained aikido and karate. Hans Greger mainly trained in Budokwai Stockholm and in Lidingö Ju-jutsuklubb which he started in 1983.

Over the years, Hans Greger has had many assignments in ju-jutsu both in Sweden and internationally. He was chairman of the Swedish Budo Association's Ju-jutsu section between 1973 and 1998. From 1991 to 2022 he was chairman of the Swedish Ju-jutsu Association, which from 1999 served as the style organisation for the Ju-jutsu Kai style, where Hans Greger from the start was style director. He has been part of the national grading committee since its inception in 1970 and thereby graded over 2,500 new black belts and higher dan grades. Hans Greger co-founded the European Ju-jitsu Federation in 1977, which then became the basis for the International Ju-jitsu Federation. In 1987, he received the National Sports Confederation's highest badge of merit from Prince Bertil.