Undrafted, Holmstrom signed a two-year entry-level contract with the Philadelphia Flyers on March 17, 2010 after playing four seasons of collegiate hockey with UMass Lowell.

[2] On July 3, 2014, Holmstrom left the Flyers organization after four years to sign a free agent contract with the Carolina Hurricanes.

As a free agent in the off-season, Holmstrom approaching his 12th professional season opted to sign abroad by agreeing to a one-year contract with Norwegian club, Lillehammer IK of the Eliteserien on June 16, 2020.

Holmstrom opted to return to North America following the season, agreeing to continue his career in the ECHL with the South Carolina Stingrays on August 13, 2021.

[9] In July 2022, Holmstrom joined the Orlando Solar Bears of the ECHL as an assistant coach, effectively ending his playing career.