The Swiss youngster played just 45 minutes for Manchester United.
His arrival will be the second Premier League fringe player to make his way to Celtic from Manchester this summer, with Belgian Dedryck Boyata leaving Manchester City and heading to Glasgow earlier this summer.
Janko has trained with the Manchester United first-team in the past and considering their lack of right-backs it is perhaps surprising to see him being let go so easily, and cheaply.
Janko however struggled to impress on his only first-team fixture for Manchester United. He was subbed off after just 45 minutes of the now infamous 4-0 League Cup defeat to Milton Keynes Dons.
The Swiss under-19 international did however impress at the start of a loan spell with Bolton Wanderers, where he was managed by former Celtic boss Neil Lennon.
Will Janko be a first-teamer?
He certainly has competition. Boyata can play right-back, as can Efe Ambrose. Then he also has returning Mikael Lustig, young Darnell Fisher and Adam Matthews to compete with.
Much may depend on the future of the latter. The Welshman was linked with a move away from the club last month.