Channel 5's 90-minute broadcast of the reality show, culminating in Paula Hamilton's departure, pulled in 2.1m (8.8%) from 9pm and 169,000 on +1, which matches the numbers for the opening eviction programme from last year.
5's Big Brother pipped Channel 4's One Born Every Minute, which held 2.07m (8.1%) in the 9pm hour as well as 303k on timeshift - rating as the broadcaster's most-watched show of the night.
However, the Richard Desmond network lost out to BBC Two, which also managed 2.1m (8.7%) for 8pm's Stargazing Live. Some 1.63m (6.8%) stayed up past 9.30pm on Two for World's Most Dangerous Roads.
Midsomer Murders boosted ITV by rising nearly 600k week-on-week to 5.69m (23.4%) between 8pm and 10pm, denting David Attenborough's Africa, which fell to a still slot-winning 5.75m (22.5%).
ITV's long-running detective drama, however, beat BBC One's 8pm offering Food Inspectors, which served up 4.05m (16.9%).
Overall, ITV1 took pole position in primetime with 23.7% (+1: 1.1%), beating BBC One's 19.6%. BBC Two followed in third place with 6.2%, ahead of Channel 5's 5.6% (+1: 0.3%), and Channel 4's 5.4% (+1: 0.8%).
BBC Three's late-night movie Armageddon was the most-watched multichannel offering of the day with 810k (6.2%) from 10pm.