Career
Bodø/Glimt
In the summer of 2007, a then 14-year-old Berntsen was selected as Bodø/Glimt"s representative to train with the best young football players in Norway and be coached by the likes of Åge Hareide and Ole Gunnar Solskjær. He joined current Rosenborg team mates, Fredrik Midtsjø and Jonas Svensson. On 13 May 2010, just a month after his seventeenth birthday, Berntsen made his senior debut when he was a 63rd minute substitution for Håvard Sakariassen in a Norwegian Cup game against Innstranden.
In September 2010, Berntsen signed a professional contract with Glimt.
He made his Adeccoligaen debut a week later when he came on for Runar Berg against Sandnes Ulf. The following day, Berg, one of Glimt"s most famous players, retired with immediate effect.
He explained the decision by stating, "when I saw Daniel Berntsen running down to the byline for the second time and putting a ball across the front of goal, it became very clear to me: I cannot take up a space in the team at the expense of such a talented youngster." Berntsen went on to start four of the last five games in the 2010 season. In 2011, Berntsen became the second most regular starter for Glimt, starting all but the first three games in the season.
His first professional goal was, surprisingly, from a back post header in a 2–1 over Strømmen on 5 June 2011.
In mid-August, Berntsen himself confirmed to Norsk Rikskringkasting that Tromsø wanted him to replace Ruben Yttergård Jenssen if the latter were to leave for an unnamed Dutch club Such a deal would not develop, however, and on 31 August 2011 Berntsen signed for Norwegian giants Rosenborg for 4.5 million kroner. Berntsen stayed with Glimt until the end of the season, scoring a further two goals in the process.
His last game, like his debut, came against Sandnes Ulf on 30 October 2011.
Rosenborg
After signing a four-year deal with Rosenborg, Berntsen admitted that the move "is a dream come true." After being compared to former Glimt and Rosenborg hero Runar Berg, the man he had made able to retire, he said, "it"s great to be compared with such a great player. We can only hope that I have some of the same qualities." His first on-field contribution to his new club came on 2 November 2011 when he played in the under-19 side"s 4–1 loss to Aston Villa in the 2011-2012 NextGen series.
On 25 April 2012, Berntsen was signed on a one-month loan by Fredrikstad. Berntsen was again loaned out in August 2012, this time to his old club Bodø/Glimt until the end of the 2012 season.
Berntsen did not receive much playing time after he returned to Rosenborg.
He started his first match in the 3–2 victory against Odd, where he also scored the match-winning goal.
