Born in Zwolle, Overijssel, Jans joined Groningen on 2002, and was the longest-serving head coach in the whole Eredivisie, being instrumental in the club's recent successes, including two consecutive UEFA Cup qualifications in 2005 and 2006.

[1] In November 2009, he announced he would leave Groningen at the end of the 2009–10 season, after eight years in charge of the club, citing his desire for a new experience as the main reason behind his choice.

Jans' first season in charge of Heerenveen was mostly considered as disappointing, as he only managed to achieve an unimpressive twelfth place in the league table and was also criticized due to a number of controversial choices.

His second season turned out however to be much better, thanks to his ability to get the most out of forwards Bas Dost, Luciano Narsingh and Oussama Assaidi and drive the team into the battle for the league title by April 2012.

[6] FC Cincinnati officially announced the hiring on 5 August 2019, ending a months-long coach search that began with their firing of Alan Koch in May 2019.