A graduate of the Montana Military Academy and United States Army Military Police Academy, Giacometto served in the United States Army and Army Reserve[6] from 1980 through 2003[7] before retiring as a lieutenant colonel.[6]
In 1987, Giacometto was elected to the Montana House of Representatives, where he served until 1990.[7]
On February 28, 1990, President George H. W. Bush nominated Giacometto as US marshal for Montana. On April 5, the United States Senate unanimously confirmed him,[8] making Giacometto the then-youngest US marshal in history.[2] He left the Marshals in 1993,[7] before his four-year term was complete.[8] Giacometto was also a magistrate judge.[6]
Giacometto was the Montana Department of Agriculture director from 1993 through 1995[7] under Governor Marc Racicot.[2]
In 1995, Giacometto became the chief of staff for US Senator Conrad Burns,[2] working out of the Dirksen Senate Office Building.[9] After a national magazine identified Giacometto as the single congressional staffer "who took the most junkets at the expense of industry and other private interests", he left Burns' employ in 1999 to become a lobbyist for Morrison–Knudsen.[2]
Upon the election of Governor Judy Martz, she appointed Giacometto to one Montana's two seats on the Northwest Power and Conservation Council (NPCC), where he annually earned US$87,600 (equivalent to $159,280 in 2025).[2] In 2001, Giacometto submitted a falsified travel invoice in connection with his appointed duties, for which he was being prosecuted in 2002 by the Lewis and Clark county attorney;[10] he was acquitted of the misdemeanor in January 2001 by a six-member jury. That August, Giacometto was the first person at the scene of the drunk-driving crash that killed Montana Representative Paul Sliter, and was seen "trying to hide beer cans and bottles that had spilled from [Shane] Hedges' wrecked pickup, in which Sliter had been riding."[3] Giacometto was also the subject of investigation by Lewis and Clark County law enforcement officers for allegedly threatening Missoulian columnist Mary Jo Fox (through state senator John Harp) for an article critical of the governor.[2] Giacometto left the NPCC seat in March 2002.[3]
In 1999, Giacometto became the vice president of government affairs for both Washington Group International (until 2001) and Morrison–Knudsen. In 2005, he was a lobbyist for the Vector Group.[7]