A regular series of thirteen episodes was broadcast weekly in 2006, starting with "New Earth" on 15 April and concluding with "Doomsday" on 8 July.

The Doctor continues to travel with his companion Rose Tyler (Billie Piper), with whom he has grown increasingly attached.

[13] In 2005, Tennant had starred in Casanova, written by Russell T Davies and produced by Julie Gardner, when he was offered an audition as the Doctor, which surprised him as it had not yet been publicly announced that Christopher Eccleston would not be returning to the role.

He was offered the role at Davies's home, and was initially concerned that if the series was not recommissioned he would become known as "the person who played the Doctor for 35 seconds".

[23][24][25] Shaun Dingwall returned for several episodes as Pete Tyler and Penelope Wilton reprised her role as Harriet Jones for the Christmas special.

[28] Elisabeth Sladen featured in the episode "School Reunion", returning to the character of Sarah Jane Smith, companion of the Third and Fourth Doctors.

[29] Other guest stars included Adam Garcia and Daniel Evans in "The Christmas Invasion",[32] Anna Hope and Adjoa Andoh in "New Earth",[33][34] Anthony Head in "School Reunion",[30] Roger Lloyd-Pack in "Rise of the Cybermen" / "The Age of Steel",[35] Rory Jennings, Margaret John, and Maureen Lipman in "The Idiot's Lantern",[36][37][38] Claire Rushbrook in "The Impossible Planet" / "The Satan Pit",[39] Nina Sosanya in "Fear Her",[40] and Raji James and Barbara Windsor in "Army of Ghosts" / "Doomsday".

[53] New writers for the show included Toby Whithouse,[54] Tom MacRae,[55] Matt Jones,[50] and Matthew Graham.

[57][58] Stephen Fry was due to write the eleventh episode, but was forced to withdraw as he could not complete the script in time.

[62] "The Runaway Bride", which was supposed to be the midway point of the original line-up, was moved early on to be the Christmas special for the next series, and was replaced by "Tooth and Claw", which had its roots in a story about "Queen Victoria and a werewolf", something Davies had been contemplating since 2004.

[66] However, the team had learnt from the first series about the specific challenges faced by a sci-fi series; instead of last-minute changes to reduce CGI, plots were written in mind to use shots needing less CGI: gardens and concrete plazas, such as those employed in the then-recently released Battlestar Galactica show, which allowed an equitable budgetary distribution between stories.

[73] In "The Christmas Invasion", it is revealed to be a secret organisation which possesses alien technology,[74] and its establishment is shown in "Tooth and Claw", whose late addition to the series allowed Davies to fix it in British history by associating it with Queen Victoria .

[72][75] References then gradually started appearing in the script of every episode: blocked websites, mentions of buildings and archives owned by Torchwood and so on.

[68] Contemporary Torchwood is finally visited by the Doctor and Rose in "Army of Ghosts" / "Doomsday", at which point it is situated within London's Canary Wharf and accidentally allows the invasion of the Cybermen and, subsequently, the Daleks.

[90] Maureen Lipman appeared in "The Idiot's Lantern", but due to scheduling conflicts, recorded her scenes remotely in London.

[96] The cues from the first series were re-recorded by the BBC National Orchestra of Wales, the original music having been created using orchestral samples.

[101] A Children in Need special and an interactive episode, entitled "Attack of the Graske", were both released alongside the series.

[6] These mini-episodes (approximately 60 seconds in length) served as prequels to each forthcoming episode, and were available for download to mobile phones and viewable at the official Doctor Who website.

[109] The major promoter for the series, aside from the BBC, was Radio Times: they released their first programme-specific Christmas double issue in 16 years, instead of the usual generic issue, for the release of The Christmas Invasion,[109][113] a special section called "Doctor Who Watch",[111][112] and covers and interviews with cast and crew throughout the run of the series.

[142][143] Series 2 holds a 100% approval rating on Rotten Tomatoes with an average score of 9/10, based on eight critic reviews.

[144] Many considered the finale "Doomsday" one of the best episodes[145][143][146] and "Fear Her" one of the worst,[147][148] with one reviewer calling the series full of intense highs and lows for both the characters and the plot.

[145][154] However, they both still found the finale enjoyable: Wilkins calling it "supremely entertaining television", and Ruediger stating "it makes no attempts to play by any rules other than its own" and provides a "gut-wrenching farewell" for Rose.

[143] In addition, IGN's Haque, while finding "the denouement to be the clear emotional highlight", also found the dialogue "funny and witty" and adding to "the memorability of the finale".

Together with "the great writing and beautiful acting", he called it more entertaining than entire seasons of many shows and "sci-fi television at its finest".

[146] Similarly, Radio Times's Braxton praised the show for finding "ways to think big" since its revival while also sometimes delivering on this scale "with such devastating intimacy".

[143] Screen Rant's Edward Cleary ranked the series sixth of thirteen, and felt the chemistry between Tennant and Piper—one of Doctor Who's best duos—overshadowed any problems; he described "The Impossible Planet" / "The Satan Pit" as one of the "best two-parters ever".

[142] In 2021, Comic Book Resources's Gabriela Delgado noted the series was the second-highest rated on IMDb of Doctor Who's modern run, behind only the fourth.

[156] Den of Geek's Andrew Blair placed the series nineteenth overall, the lowest of Tennant's run, and believed it was a "comedown" in quality from its predecessor.