Fahey was drafted in the 8th round, 212th overall, by the San Jose Sharks in the 1998 NHL Entry Draft. Before becoming a professional hockey player, Jim was a member of the Dorchester, MA, Tier 2National Championship Midget Team in 1996, and subsequently a standout at Catholic Memorial High School, winning MVP awards while leading his school to four straight state championships. He went on to become a star at Northeastern University, where he finished his career with the single season defense scoring record for the Huskies as a First Team All-American and Hobey Baker Award finalist. During his draft year, he was featured in a segment with his idol, Raymond Bourque, in a feature for NHL on Fox. Following his college career, in the 2003 season, after spending some time with San Jose's AHLfarm team in Cleveland, Fahey was recalled to the Sharks and was selected San Jose's rookie of the year. Despite spending nearly half the season in the minor leagues, he led all rookie NHL defenseman in scoring. In the 2004 season, Fahey battled with pneumonia, and after recording only two points in fifteen games, was sent down to Cleveland, where he played for the remainder of that season, and has seen only sporadic NHL duty since. Fahey has also played in international competitions, like the 2003 IIHF Men's World Championships. He has been named to the PlanetUSA AHL All-Star team. Fahey re-signed to a one-year contract worth US$500,000; on July 15, 2006. Prior to the 2006–07 NHL season, Fahey was traded with Alexander Korolyuk to the New Jersey Devils for Vladimir Malakhov and a conditional first round pick. On July 27, 2007, Fahey signed with the Chicago Blackhawks and spent the full year with the Rockford IceHogs of the AHL. On March 26, 2008, Fahey signed with German team, the Krefeld Pinguine of the DEL. On July 6, 2010, after two seasons with Krefeld, Fahey signed a one-year contract with fellow DEL team, Thomas Sabo Ice Tigers. However, only three weeks later on July 24, Fahey terminated his agreement with the Ice Tigers due to personal reasons and remained in America. Fahey also has a degree in real estate development from Northeastern University.