Undrafted, Grimaldi was a part of the United States National Team Development Program from 2002–04, He had won one gold medal at the four nations cup and an International Ice Hockey Federationsilver medal in Minsk, Belarus at the world championships before enrolling at the University of Nebraska Omaha of the CCHA. In the 2004–05 season Grimaldi scored 21 points and was named to the CCHA All-Rookie Team. Also USCHO.com named him to the all-rookie team. The University of Nebraska Omaha named him most consistent player with +24 plus/minus leading all of college hockey in the 2004–2005 season. In his second year with the Mavericks, he left for major junior hockey in the Ontario Hockey League with the Ottawa 67's. While he was with the 67's he signed with the New York Islanders and played exhibition games with the islanders before getting sent back to ottawa for future development for his overage year. In the 2007–08 season, Grimaldi turned pro officially and signed with the Rochester Americans and was later sent down to the Elmira Jackals of the ECHL. Grimaldi played in 36 games recording 15 points as a rookie with the Jackals, and made his AHL debut with the Rochester Americans and Albany River Rats. On January 15, 2008, Grimaldi was traded to fellow ECHL team the Fresno Falcons, affiliate to the San Jose Sharks. He was then later flipped to the Gwinnett Gladiators on February 19. He then played for his sixth team in the year when he was called up to the Peoria Rivermen affiliate for the St. Louis Blues. During his four game stint he recorded one assist in the last four games of the season. Grimaldi started the 2008–09 season with the Cincinnati Cyclones of the ECHL before returning to the Jackals placing third on the team with 101 penalty minutes. He attended Elmira's training camp prior to the 2009–10 but because of his previous ankle injury from the year before was not cleared to play yet, and later signed a contract midway through the season on December 12, 2009. However, after playing in 33 games with Elmira he then quit the team for reasons unknown on March 17, 2010. Later in his career, Grimaldi joined the Nottingham Panthers of the Elite Ice Hockey League for the 2013–2014 season. He played 7 games before being released, tallying 8 points. During his brief stint, Grimaldi racked up 110 penalty minutes. The Edinburgh Capitals of the same EIHL league chose to bring him back for the 2014–15 season. Grimaldi played until his release on January 4, 2015 stemming from an incident the previous evening. On January 3, 2015, playing against his former team the Nottingham Panthers, Grimaldi took exception to Max Parent of the Panthers in which he was seen to spear the player intentionally with his stick, almost going for a second attempt. He then proceeded to remove his helmet and throw it at Parent's face, following immediately with a punch to the face and dragging him to the ground. Parent picked himself up and eventually toppled Grimaldi. Thrown out of the game, picking up 67 minutes' worth of penalties, Grimaldi was released the following day amidst the impending ban confirmed days later by the DOPS of 18 games.
