After marrying a Greek citizen, the weightlifter Giorgos Tzelilis, Manjani received Greek citizenship and represented Greece at the 1997 World Championships in Athletics in Athens. Her first major success came in 1999 in Seville, where she won the gold medal at the World Championships with a throw of 67.09 m. Her performance was considered as a world record, as a new type of javelin had been introduced in 1999. At the 2000 Summer Olympics she won the silver medal with a personal best of 67.51 m. She also won the bronze medal in 2004. Maniani is also a European champion and double world champion. Her personal best throw of 67.51 metres is the current Greek record.