Background
He was born in Oslo, and started his career in Strømmen before he moved to Lillestrøm where he played 65 matches in Tippeligaen from 1993 to 1996.
He was born in Oslo, and started his career in Strømmen before he moved to Lillestrøm where he played 65 matches in Tippeligaen from 1993 to 1996.
As a player, Berntsen is most notable for his time at Lillestrøm and Vålerenga in Tippeligaen and the Austrian club Bregenz. After his retirement he has been head coach of Lørenskog, Kongsvinger and Strømmen. In 2000, Berntsen moved to the Austrian club Southwest Bregenz, where his former teammate from Lillestrøm, January Ove Pedersen also were playing.
After playing three matches in six months for Bregenz, he was loaned out to Bryne where he played five matches in Tippeligaen before he retired after one season with Bærum in 2001 Norwegian Second Division.
In 2006, Berntsen was the head coach of the third-tier club Lørenskog and John Carew"s youth club was fighting promotion alongside Notodden. Even though Lørenskog was not promoted, Berntsen was head coach of a second-tier team in 2007 since Kongsvinger hired him as Vegard Skogheim"s successor on 6 November 2006.
Berntsen led Kongsvinger to a strong fourth place in 2007 Adeccoligaen, two points behind Bryne which played promotion play-official With two points in the six first matches of the 2008-season, and Kongsvinger positioned at the bottom of the table, Berntsen was fired on 7 May 2008.
On 3 August 2008 he was hired as head coach of his youth-club Strømmen, and saved the club from relegation to Norwegian Third Division.
Ahead of the 2009-season, Petter Myhre was named co-coach together with Berntsen. In 2010 Strømmen finished three points behind the play-off promotion. The next season, Myhre had resigned from the job at Strømmen and was replaced by Andreas Holter which would be leading Strømmen together with Berntsen.
In July 2011, Nettavisen named Berntsen as one of the most talented football-coaches in Norway.
Berntsen"s contract ended after the 2011-season, and he was replaced by Erland Johnsen. In December 2011, Berntsen was linked to the vacant job as head coach of the Tippeliga-club Stabæk, but according to Norwegian television 2 Berntsen recejeted Stabæk"s offer.
He then moved to Vålerenga where he played 45 league-matches between 1997 and 1999 and also won the Norwegian Football Cup in 1997. In the decisive match of 2006 Norwegian Second Division, Notodden won 5–3 against Lørenskog at home, and was promoted to Adeccoligaen. With Berntsen and Myhre as coaches, Strømmen won their 2009 Norwegian Second Division group and was promoted to Adeccoligaen. In the decisive match of the 2011-season, Strømmen avoided relegation with a 6–1 win against Nybergsund.