The BBC reported Saturday that during the final moments of Friday's show, viewership rose to 10.6 million as Tennant, 38, was replaced as the Time Lord by actor Matt Smith.
"I don't want to go" were Tennant's last words on the popular science fiction series.
The Time Lord of "Doctor" fame changes his appearance when he regenerates, meaning a new actor steps into the role as the series progresses. Smith, 27, represents the 11th incarnation of the lead character.
Smith made a brief appearance in Friday's episode and is to star in his first full-length episode later in 2010.
The BBC said while the "Who" episode won its time slot by drawing more viewers than "Coronation Street," both series were bested on the day by the 11.6 million viewers who watched a New Year's Day episode of "EastEnders."