He appeared in the spin-off television show Torchwood.
-> In-universe, he used his vortex manipulator to travel back in time to catch up with the Doctor again. Aiming for the early 21st century, he miscalculated and ended up in the mid-19th century. As he was now immortal, he set himself up as an agent of Torchwood and waited for the Doctor. Just over 150 years later, after the fall of Torchwood One at Canary Wharf, London ("[[tardis: "Army of Ghosts"|Army of Ghosts]]/[[tardis: "Doomsday"|Doomsday]]") he relocated the headquarters of the organisation to Torchwood Three in Cardiff and rebuilt it in the honour of the Doctor, a strategeic location due to the presence of a space-time rift which the Doctor uses to refuel the TARDIS. A few years later, the TARDIS arrives and Jack runs after and grabs onto it, ending up on the planet "Utopia" ("[[tardis: "Utopia"|Utopia]]") before returning to Earth with the Doctor to confront the Master ("[[tardis: "The Sound of Drums"|The Sound of Drums]]/[[tardis: "Last of the Time Lords"|Last of the Time Lords]]"). He then returns to Torchwood, until approximately a year later when the Earth was invaded by the Daleks ("[[tardis: "The Stolen Earth"|The Stolen Earth]]/[[tardis: "Journey's End"|Journey's End]]"), returning again to Torchwood once he had helped the Doctor defeat the Dalek invasion. He disbanded Torchwood and left Earth after the death of Ianto Jones during the incident with the 456, and later encountered the Tenth Doctor for the final time in a space bar ("[[tardis: "The End of Time"|The End of Time]]"). Most recently, he returned to Earth to be reunited with former Torchwood colleague Gwen Cooper to deal with the "Miriacle Day" case, and is apparently currently based in the USA.