As a youth he played basketball, soccer, beach volleyball and tennis, but shifted to swimming at the age of ten.

Raised as a breaststroker, after 2000 he dedicated totally to freestyle swimming, soon to achieving noteworthy results.

Magnini gained his first international honour in 2003, with a silver medal in 100 m freestyle at the European Swimming Championships (short course) in Dublin.

[5] His steady rise reached its highest point at the 2005 World Aquatics Championships, where he won the gold medal in the men's 100 m freestyle with the time of 48.12, then the all-time second fastest behind Pieter van den Hoogenband's world record.

[7] On 8 July 2019, it was reported that Magnini saved newlywed Andrea Benedetto from drowning off a Sardinian beach.