This year's ceremony, hosted by Kylie Minogue, James Corden and Mat Horne, averaged 5.18m (21.7%) for ITV1 between 8pm and 10pm.
Last year's Osbournes-fronted show pulled in around 6.1m in the same slot on February 20, 2008.
Big winners at this year's event included Welsh singer Duffy, with three awards, and US rock act Kings Of Leon, with two.
> Live Blog: Brits 2009
ITV1 was in front of the competition throughout primetime, finishing up with an average audience share of 23.8% to BBC One's 18.7%.
Before the Brits, Emmerdale had pulled in 6.92m (32.3%) and Coronation Street had drawn 9.15m (40%).
Waterloo Road took 3.83m (15.9%) for BBC One in the 8pm hour, a week-on-week fall of around half a million, then Nature's Great Events interested 4.45m (18.7%).
Channel 4's popular property block of programming also took a slight dent from The Brits. Relocation, Relocation appealed to 2.82m (11.7%) at 8pm, then Grand Designs managed 3.09m (13%).
The penultimate episode of eco show It's Not Easy Being Green pulled in 1.99m (8.4%) for BBC Two at 8pm, then the latest MasterChef grabbed 3m (12.3%). Documentary Trouble In Amish Paradise, about the Old Order Amish of Pennsylvania, averaged 2.2m (9.3%) for the 9pm hour.
Live coverage of Villa's clash with CSKA Moscow in the Uefa Cup averaged a decent 1.57m (6.9%) for Five between 6.30pm and 9pm. Following on, the third episode of Minder brought in 1.39m (5.9%), a fall of over 400k on last week.
Elsewhere, Hollyoaks put in 1.61m (7.8%) for Channel 4 at 6.30pm, and on Five, Neighbours had 1.63m (10.3%) and Home & Away had 1.16m (6.1%).
Channel 4 averaged out to 9.2% in primetime for third place overall, with Channel 4+1 adding a further point. BBC Two had 8.1% for fourth, while Five was last with 6.9%.
Ratings data supplied by Attentional