The green light from the Premier League has now been received, meaning the 30-year-old moves to West Ham on a free transfer.
Related ArticlesLiverpool to offer Babel in exchange for ColeSpurs eye last-ditch Parker bidMan Utd 3 West Ham 0Man Utd v West Ham: LiveMan Utd v West Ham previewNullifying Scholes a priorityJacobsen has earned 35 caps for his country and played 16 times for Blackburn after joining them on a free transfer from Everton last summer.
Hammers boss Avram Grant, whose side have shipped nine goals in their opening three Barclays Premier League games, had made recruiting a new right-back a priority.
Jacobsen began his career at Danish side Odense and and played for Hamburg, FC Copenhagen and Nurnberg before joining Everton two years ago.
His appearances for the Toffees were limited by a shoulder injury and he was allowed to leave after one season.
Jacobsen played in all three of Denmark's matches at this summer's World Cup, where they failed to progress from their group.