Originally drafted by the Red Wings in the seventh round (196th overall) of the 2014 NHL Entry Draft, Holmstrom skated in 44 games for Skelleftea of the Swedish Hockey League in this season, recording 20 points (10-10-20) and four penalty minutes. The 18-year-old forward ranked ninth on the club in scoring and tied for second overall in the SHL among junior-aged players. Holmstrom helped Skelleftea reach the SHL finals and led the league in postseason scoring with 18 points (7-11-18) in 15 games, breaking the league record for playoff points by a junior player. After the season, he was named the Swedish Junior Hockey Player of the Year. The Arvidsjaur, Sweden, native also represented his country at the 2015 IIHF World Junior Championship in Toronto and Montreal, ranking fifth on the team with seven points (1-6-7) in seven games.

The 6-foot-1, 198-lb., forward spent the 2013-14 campaign with Skelleftea’s junior club, recording 38 points (13-23-38) in 33 games and making his men’s league debut with four regular-season games in the SHL. He totaled 45 points (17-28-45) and 12 penalty minutes in 46 games at the under-20 level from 2012-15 and notched 47 points (12-35-47) and six penalty minutes for Skelleftea in the under-18 circuit from 2011-14.