František Jež débuted on the World Cup circuit at the end of 1987 during the Four Hills tournament. During his career, which lasted until 1999, Jež competed at two Olympic Games (1992/1998) and three World Championships (1991, 1993, 1995). He won a team bronze at the 1992 Olympic Winter Games and team silver at the 1993 World Championships. His best individual finish at those tournaments was 13th on large hill at the 1992 Olympics. Jež also won four individual World Cup races, all during the 1989-90 season, when he also placed fifth overall, his best overall World Cup finish. After finishing his sporting career, Jež worked as a used cars dealer and gas station owner. During the early 2000s, he was also assistant coach of the Czech national team and manager of the best Czech ski jumper in the 2000s Jakub Janda.