The show’s nail-biting fifth series finale on Sunday May 5 attracted a TV audience of 12.1 million, according to new figures.
This is enough to rank it above some of the decade’s other big-hitters, such as Broadchurch and Call the Midwife.
But it’s not quite in the same league as Bodyguard, whose finale last year enjoyed a TV audience of 14.3 million.
Bodyguard remains this decade’s most-watched drama series, followed by Doctor Who, Sherlock and Downton Abbey.
Official ratings for Line of Duty’s finale have been published by Barb.
They include people who recorded the episode and watched up to seven days later.
Besides the TV audience of 12.1 million, an additional 600,000 people saw the finale on other devices such as laptops and smartphones.
The new figures mean two of this decade’s top five dramas - Line of Duty and Bodyguard - are the work of one writer, Jed Mercurio.
Both series were broadcast on BBC One, though the production company behind them - World Productions - is owned by ITV.
Bodyguard’s finale in 2018 attracted the biggest TV audience for a drama series since 2001.
Here are the most-watched TV dramas of the decade so far, by highest rated episode:
1. Bodyguard (BBC One), September 23 2018: 14.3 million
2. Doctor Who (BBC One), November 23 2013: 12.8 million
3. Sherlock (BBC One), January 1 2014: 12.7 million
4. Downton Abbey (ITV), November 6 2011, 12.5 million
5. Line of Duty (BBC One) May 5 2019: 12.1 million
All figures are consolidated ratings for audiences watching on TV.