Millions of viewers tuned in to ITV for the two separate programmes at 1845 GMT and 2115 GMT, which saw the triumphant five band members chosen from 10 finalists.
The early show drew an average of 8.7 million while the climax of the series, when the five winners were revealed, drew an average 11 million viewers.
The second instalment of Popstars drew almost two million more viewers than Who Wants to be Millionaire? - usually ITV's top scoring show on Saturday night.
In comparison, last Saturday's single episode of Popstars at 1815 GMT - which has been running for several weeks - drew an average audience of 8.5 million.
An ITV spokesman said the viewing figures were "fantastic".
"It's particularly strong among the 18-34 age group and it's certainly gripping the nation," he said.
Jim Davidson's Generation Game on BBC One, also at 1845 GMT on Saturday, fared poorly with average ratings of six million.
Comedy detective series Jonathan Creek also lost in the 2100 GMT to 2200 GMT slot. It took an average rating of 5.7 million - its usual score.
The ratings figures demonstrate how interest in Popstars has increased over the weeks.
Build-up
The series began with thousands of hopefuls being auditioned, gradually whittled down until the final five were revealed on Saturday's show.
Popstars was the latest variation on the theme of so-called reality TV - made popular in the UK by the summer sensation Big Brother.
Audience interest in Popstars was fuelled by the continued fascination with the trials and tribulations of others, in this case the thousands who sweated through the live televised auditions.
The media has once again devoted column inches to dissecting - and often ridiculing - the programme and those taking part.
The excitement and banter over Popstars seems to have paid off - its finale attracted more viewers than Big Brother's final show.
An average of nine million people tuned in to watch Craig Phillips take the £70,000 prize-money in September.
However, the figure was Channel 4's best ever for a Friday evening and the highest by that time last year.