Giannelli became head golf coach at Connecticut in the fall of 1981 and held that position for 20 years until the summer of 2000. He continued to serve as coach emeritus for the UConn golf team until his death.
He led UConn to the BIG EAST Championship in 1994 and the ECAC Championship in the fall of 1993. Giannelli guided UConn to top 10 finishes in 97 of the 124 tournaments he coached the Huskies. UConn won four New England Championships in the fall of 1982, spring of 1993, fall of 1994 and spring of 1997 under Giannelli.
Giannelli was honored as the BIG EAST Conference Coach of the Year in 1994-1995 and was named the New England Coach of the Year in both 1992 and 1994. He was named the 1992-1993 District I Coach of the Year by the Golf Coaches Association of America, and in 1993-1994 won both ECAC Coach of the Year and NCAA District I Coach of the Year honors.
Coach Giannelli served as President of the New England Intercollegiate Golf Association in 1988 and in 1992 was presented the Gordon McCullough Award by the NEIGA for contributions to the game.