The Czech climber turned pro with the CCC Sprandi Polkowice team in 2015, so will be heading to a familiar environment after the Pro Continental team merged with the old BMC Racing team at the end of last year to form CCC Team.
Highlights of his first stint in orange included a win and a podium at the Tour of Austria, and 12th overall at the 2017 Giro d'Italia.
Hirt's climbing prowess secured him a move to Astana last season, where he has played a support role for Miguel Ángel López at the Giro d'Italia and Vuelta a España.
At this year's Giro, Hirt narrowly missed out on taking a stage win on stage 16, with Giulio Ciccone outsprinting the 28-year-old in Ponte di Legno. This season has also seen him finish fifth at the Tour de Suisse and seventh at the Tour of the Alps.
"We have been busy recruiting riders who are solid climbers and can really strengthen our ability to go for the General Classification from 2020 onwards, which is something we have lacked this season, so we are looking forward to welcoming Jan Hirt to the team," said CCC Team general manager Jim Ochowicz.
"Jan is often one of those riders who flies under the radar but is consistently up there with the best on the General Classification and his results this year, with fifth at the Tour de Suisse and seventh at Tour of the Alps, are a testament to his ability as a stage race rider."
CCC Team are also adding Ilnur Zakarin from Katusha-Alpecin and Fausto Masnada from Androni Giocattoli-Sidermec, as the team look to boost their stage racing capacity. German 21-year-old Georg Zimmerman, who recently finished fifth at the Tour de l'Avenir, will also race for the team next season.
"Given Jan raced with CCC Sprandi Polkowice until 2017, he is very familiar with many of the staff and riders who are now part of CCC Team so we have no doubt he will fit in well with the team," Ochowicz continued.
"Jan already has a lot of experience as a professional rider but we believe his best is yet to come and we are excited to see how Jan continues to develop over the next two seasons while working with our performance team."
Along with Hirt, Zakarin, Masnada and Zimmerman, the team has already announced the addition of versatile sprinter Matteo Trentin.