Danish defender Jens Berthel Askou joined Norwich City on 30th July 2009 signing a two year contract following a successful trial on Norwich's pre-season tour of Scotland.

Askou began his career at Ikast FS before moving to Holstebro BK in 2002. His performances led to a contract with 1st Division Silkeborg IF in the summer of 2003, following a successful trial. He helped the club regain promotion to the Danish Superliga during his first season, and became a regular for four years. In 2007, Askou failed to agree a new deal with Silkeborg, which led to a move to Turkish football with Kasimpasa. Despite Kasimpasa winning promotion to the Turkish top flight, Askou's contract was not renewed and as a free agent, joined Norwich on trial

Jens made his debut for Norwich in the 4-0 away win over Yeovil on 11 August 2009 in the Carling Cup. He finished the season with 27 appearances and 2 goals

With Elliott Ward, Leon Barnett, Michael Nelson and Zak Whitbread ahead of him, Askou was alllowed to join Millwall on a month's loan on 19th January 2011 although he wasl not permitted to play against Norwich when the Lions travel to Carrow Road. Askou was sent off on his debut for Millwall, in a 4-2 defeat to Leicester, and was suspended for three games and thus did not play again for the Lions returning to Norwich on 24th February 2011. He made 5 appearances for Norwich during 2010/11

Jens was released by Norwich on 1st June 2011 along with Matty Gill and Sam Habergham

On 26th August 2011, Jens signed for Vejle Boldklub Kolding in his native Denmark.

On 2nd August 2013 Askou signed a 2 year contract with Esbjerg. Having hoped to bring Vejle back to the best Danish tier, Askou saw this dream difficult following Vejle's economic struggle, and following his transfer to Esbjerg, he expressed joy over playing in the Danish Superliga once again. He had played 55 times for Veijle scoring six goals. He made just 21 appearances for Esbjerg, 19 of which were in 2013/14 including six games in the Europa League. He moved to third tier Skive IK in 2015 becoming player/assistant manager before taking up a similar role with Thisted FC the following year. In June 2017, he became Erik Rasmussen’s assistant at Danish side Vendsyssel. He took charge of Vendsyssel on May 8 when Rasmussen resigned. Askou secured their place in the 1st Division (second tier) play-offs which they then won against Lyngby on May 27. They are now in the inaugural season in the Danish Superliga.

Askou was sacked by Vendsyssel in May 2019 following a relegation play-off defeat to AC Horsens leading to their relegation.

In October 2019 he joined Danish four tier side TIF All Stars

In the beginning of November 2019 it was confirmed, that Askou would become the manager of HB Thorshavn in the Faroe Islands starting from the 1st December 2019.

On 7th January 2021 he was appointed manager of Danish side AC Horsens

In June 2023 he left Horsens to become manager of Swedish top flight side IFK Gothenberg.