The club spent the next forty years in lower division anonymity, before favourable economic circumstances enabled them to gain promotion to Allsvenskan in 1968, although they were relegated after just one season.

The high point was arguably in the years 1973–1974, when the club again gained promotion to the highest league and its squad contained a number of high-profile players, such as Roland Grip, then a member of the Swedish national team.

With new manager Magnus Pehrsson and prodigal son and goal-getter Olle Kullinger (starting his career with IF VP and later also having played with Enköpings SK, Halmstads BK and IF Brommapojkarna in Superettan and Allsvenskan) bearing the captaincy, the club finished the season in second place, which meant they had to qualify to gain promotion to Superettan.

Millqvist and Sundgren was sacked after the first six games and youth-team coaches Johan Mattsson and Andreas Brännström led the team for the rest of the season.

In 2010 IK Sirius played in the third tier Division 1 Norra and finished 2nd in the table 5 points behind rivals Västerås SK and as a result they went through to the Superettan play-offs, where they went head-to-head with Jönköpings Södra.

A 0–1 home defeat to Vasalund and a 1–0 away win at Enköping set the team up for an all-decisive match against second-placed Östersunds FK.

The team had been bolstered by the signing of several experienced players, including former Djurgården, Molde and Sweden midfielder Johan Arneng.

This time all the pieces fell into place as the team won the Division 1 Norra handily, securing promotion to Superettan with five games still in hand, and ending the season undefeated.

The 2014 season again began with Cup success, as Allsvenskan teams Djurgården and Halmstad were dispatched in the group stages, setting up a quarterfinal with IFK Göteborg.

In the end, however, Sirius enjoyed a successful return to Superettan, finishing in sixth place, after a season that included wins against both the two directly promoted teams, Hammarby and GIF Sundsvall.