Like his brother Marco, now a football head coach, Giampaolo started his career at Giulianova. He played his first professional season in 1987–88, and made 27 Serie C2 appearances. He then joined Juventus youth team. After age of 20, he was loaned to Spezia at Serie C1, Bari at Serie A and Verona at Serie B. In October 1993, he joined Palermo at Serie B, but in the next season he joined Serie B rival Pescara, where he played another 3 Serie B season, including 1996–97 season which scored 16 goals. In summer 1997, Genoa which failed to return to Serie A in the previous season, signed Giampaolo. He scored 10 goals but once again missed to promotion. He played 4 Serie B games at the start of 1998–99 season before joined Salernitana, newcomer of Serie A in October 1998. But Giampaolo Serie A career faced another short end due to Salernitana 1 point below relegation line. After played 2 games for Salernitana, he returned to Pescara, league rival of Salernitana. Pescara finished the least in 2000–01 season, and Giampaolo was loaned to Cosenza at Seire B before returned to Pescara at 2002–03 season, helped the club promoted back to Serie B.