Lamberti was born in Brescia, Lombardy. At six, he was advised to begin swimming to improve his light physique. At 17, in 1986, he won the first of his six Italian championships. He took part in the following 1986 World Aquatics Championships, where he reached the B final in the 200 freestyle, and took part in the Italian 4x200 freestyle relay.
The following year, now coached by Alberto Castagnetti, he established the new short course record at Bonn in the 200 and 400 m freestyle. However, he did not qualify for the finals in the same races at the 1988 Summer Olympic Games later in the year. At the 1989 European LC Championships, held again in Bonn, winning the gold medal in the 100 and 200 m freestyle; in the latter, with 1'46"69, he set the new world record, which remained unbeaten for 10 years, until Grant Hackett improved it at Brisbane in 1999. Lamberti at Bonn won another gold medal in the 4x200 freestyle.
He retired from professional swimming in 1993, and, from 2003 to 2008, was a member of the city's council of Brescia, with responsibility of sports and recreation. He later held several positions in the Italian Swimming Federation. In 2004 he was inducted into the International Swimming Hall of Fame.