The show, which saw Anita Shah become the first contestant to be fired by Sir Alan, averaged 8.11m (33.3%) during the 9pm hour.
The previous high was the series four opener, which took 6.4m (25.6%) on March 26 last year.
Spinoff programme The Apprentice - You're Fired!, which featured an interview with Shah, pulled in 3.01m (15.2%) for BBC Two in the 30 minutes from 10pm.
In the 9pm hour, The Apprentice was comfortably ahead of its nearest competitor Taggart, which drew 3.25m (13.4%) for ITV1.
Channel 4's Grand Designs attracted 2.59m (10.6%), while BBC Two's new series Alan Whicker's Journey Of A Lifetime opened to 1.99m (8.2%).
Five was last for the hour, drawing 1.42m (5.8%) with Extraordinary People: Tree Man - The Cure, a follow-up documentary to last year's story of Dede, an Indonesian fisherman with growths on his body.
ITV1 came top during the 8pm hour, pulling in 5m (21.4%) for the latest episode of The Bill, while BBC One stayed close behind, delivering 4.45m (19%) with Waterloo Road.
Over on Channel 4, 3.13m (13.4%) tuned in for the penultimate episode of Relocation, Relocation with Phil Spencer and Kirstie Allsopp.
Orangutan Diary managed 1.89m (8.1%) for BBC Two, while Five's Ice Road Truckers grabbed 1.42m (5.8%).
BBC One averaged out to 23.3% in primetime, leaving ITV1 in second place with 21.7%. Channel 4 was third with 9.6% (+1: 0.7%), followed by BBC Two with 8.2% and Five with 4.7%.
Elsewhere, BBC Four's new series Newswipe With Charlie Brooker averaged 176k (1.3%) between 10.30pm and 11pm, while a lowly 218k (1%) tuned in to watch the latest episode of Gossip Girl on ITV2.
Ratings data supplied by Attentional