Ratings for the three-hour ceremony, which do not take into account the potential audience watching in pubs and clubs, were up 700k year-on-year.
The contest was won by Norwegian folk singer Alexander Rybak by a margin of 169 points. The UK's entrant, Jade Ewen, finished fifth place with a song penned by Andrew Lloyd-Webber.
Earlier on BBC One, the penultimate episode of John Barrowman variety show Tonight's The Night put in a respectable 3.68m (34.9%).
The popularity of Eurovision helped dent ratings for Britain's Got Talent on ITV1. This week's episode, which aired from 8.20pm, averaged 9.77m (41%), a fall of over 1.3m.
Talent followed on from a new episode of Primeval, which picked up 4.53m (22.1%). Later, ITV's Best Ever Ads 2 appealed to 2.85m (12.4%).
BBC Two documentary The Best Of British Music interested 910k (3.8%) from 8.20pm, after which an extended version of Have I Got News For You amused 2.11m (9%).
On Channel 4, Lionheart: The Crusade kept 970k (4.1%) between 8pm and 9.30pm, then a screening of Kingdom Of Heaven brought in 980k (5.4%).
Five's NCIS double bill pulled in 1.01m (4.4%) and 1.38m (5.8%) from 8pm, then a new episode of CSI: NY took 1.5m (7%). Law & Order closed off prime for the channel with 775k (5.4%).
BBC One reclaimed the lead in primetime with an average share of 30.9% to ITV1's 22.7%. BBC Two was third with 8.8%, followed by Five with 5.4% and Channel 4 with 4.4% (+1: 0.4%).
Spinoff show Britain's Got More Talent notched up 1.07m (5.1%) for ITV2 at 9.20pm and 118k (0.6%) on timeshift. Two hours later, a repeat of the earlier ITV1 show gathered 727k (7.4%).
Ratings data supplied by Attentional