Hellberg takes over from Rob Edwards, who left Middlesbrough earlier this month to join Premier League strugglers Wolverhampton Wanderers. Boro currently lie second in the Championship table, seven points behind Coventry City.
Aged only 37 and with no playing or coaching experience outside Sweden, Hellberg may appear to be a left-field choice.
However, sitting second in the table will feel familiar to the Norrkoping native, as earned back-to-back runner-up finishes in the Allsvenskan in his two seasons in charge of Hammarby, who have only once finished as Swedish champions in their history.
This season, they amassed 62 points, which would ordinarily enough to win the title, but this season they were bettered by Mjallby, who smashed the Allsvenskan points record against all the odds.
Hellberg was given his chance at one of Sweden's biggest clubs having guided lowly Varnamo to 10th and fifth in their first two top-flight campaigns. Previously he worked as an assistant coach at Norrkoping, and as a player and coach in Sweden's lower leagues.
Having reportedly been in the frame to take over at Swansea City, Hellberg clearly feels that Middlesbrough are the right choice for him.
"There are many things that make Boro the perfect choice for me. The team's playing style and game idea, together with the crowd, suits me and how I want to work," he said.
Tomorrow night sees a top-of-the-table clash between Middlesbrough and Coventry on Teeside, but Hellberg will not be in the dugout. Assistant coach Adi Viveash will take charge, before Hellberg makes his bow in English football at home to Derby County on Saturday.
