Winning the first medal at the age of 19 at 1996 Summer Olympics in Atlanta, when Croatia won the first gold medal as an independent nation, he is considered the youngest debutant of the team. Losert was also the member of the golden national handball team that won the first place at the 2004 Summer Olympics in Athens. As a youngster he joined Badel Zagreb, the strongest team in the country and was part of the team who won the European Cup in 1992 and 1993. In total he won 7 league titles and 7 cups with Badel Zagreb. In 1999, Venio Losert took the plunge into Spanish handball, signing for Garbel Zaragoza (1999-2000). He later played for various ASOBAL League teams including Teka Cantabria (2000-01), BM Granollers (2001-04), Portland San Antonio (2004-05) and Cangas Frigoríficos del Morrazo. In the Portland team he won the ASOBAL League title. As one of the best goal keepers, with plenty of honours in the game, Venio Losert was given the honour to be the flag bearer in London 2012. Unlike other icons of the handball, Losert has always called himself a "normal, regular and not a showy keeper who only does what's needed to keep the ball out". Losert has always been a key part of the Croatian national team, winning also silver medals in the 1995 and 2005 World Championships. He was voted Croatias player of the year in 1997. Venio's current club is polish Vive Targi Kielce, with whom he won 10th polish cup and is one of the key players who helped the team reach the Final Four.