Sladen starred in Doctor Who from 1973–1976 and returned to the programme several times prior to the spin-off. In 2006, she made her first appearance in the revived era of Doctor Who by guest starring in the second series episode "School Reunion", which was retroactively viewed as a backdoor pilot. The Sarah Jane Adventures was the second attempt at a spin-off featuring Sladen, the first being K-9 and Company which never made it past the pilot stage in 1981. Now, living in modern-day Ealing, London, Smith investigates extraterrestrial matters and protects Earth against alien threats with a group of teenage accomplices: her adopted son Luke Smith, neighbour Maria Jackson, and friend Clyde Langer. New neighbour Rani Chandra and adopted daughter Sky Smith later join the cast. Additionally, the group is aided by Mr Smith, a sentient extraterrestrial computer, and K9, a dog-shaped robot gifted to Sarah Jane by the Doctor.
The Sarah Jane Adventures was introduced in a 60-minute special episode broadcast on New Year's Day in 2007 on BBC One. It was followed later in the year by a 10-part series, made up of five half-hour two-part serials which aired weekly from 24 September to 19 November 2007. The first serial, Revenge of the Slitheen, premiered its first part on BBC One and the second part immediately after on CBBC. For the remainder of the series, each episode first aired on CBBC and was followed by a BBC One repeat broadcast one week later. The second series, which began a trend of each series consisting of 12 episodes split across six two-part serials, had an identical release schedule with transmission occurring between 29 September and 8 December 2008. An additional special mini-episode, "From Raxacoricofallapatorius with Love", was produced in support of Comic Relief, an annual telethon used to raise funds for charity, on 13 March 2009.
For the third series, all first-run episodes were simulcast on BBC One and BBC HD twice-weekly prior to the CBBC broadcast. It began on 15 October and concluded on 20 November 2009. Original episodes then returned to CBBC for the fourth series, with repeated episodes on BBC Two, BBC HD, BBC One, and BBC One HD. It premiered on 11 October with the finale airing on 16 November 2010. Fifth and sixth series of the programme had been commissioned; however, Sladen died after only six of the intended twelve episodes for the fifth series had been recorded. Davies made the decision to continue post-production work on the completed stories, but to cancel filming on the remaining serials. The completed episodes were broadcast posthumously from 3–18 October, first airing on CBBC again followed by simulcasted BBC One/BBC One HD transmissions one week later. Three scripts had already been drafted for the other six episodes: Meet Mr Smith by Gareth Roberts and Clayton Hickman, The Thirteenth Floor by Ford, and The Battle of Bannerman Road by Davies. Davies and Ford co-created Wizards vs Aliens as a spiritual successor to the programme, in which The Thirteenth Floor was adapted as a serial. Some reruns of The Sarah Jane Adventures also aired on BBC Three or in an omnibus format. The show itself had one spin-off series, Sarah Jane's Alien Files, that aired in 2010 and a one-off reunion special, "Farewell, Sarah Jane", to honour Sladen in 2020.
A spin-off compilation series titled Sarah Jane's Alien Files aired on CBBC in 2010 to accompany the fourth series. The programme included the main characters of the parent series inputting data about recently-confronted aliens into Mr Smith. New footage was mixed with existing material from The Sarah Jane Adventures and Doctor Who.
A one-off reunion special written by Davies was produced as a webisode during the COVID-19 pandemic. It featured cast members of The Sarah Jane Adventures attending a memorial service for Sarah Jane and was released on Doctor Who social media platforms on 19 April 2020.
