Christensen replaces U.S. District Judge Don Molloy, who began serving under "senior status" last summer.
Christensen is a civil litigator who has been a partner in the firm of Christensen, Moore, Cockrell, Cummings, & Axelberg, P.C. in Kalispell since 1996.
Sen. Max Baucus submitted Christensen's name for the job to President Barack Obama back in February, and Obama officially nominated him in May.
The Senate on Monday confirmed Christensen and two other judicial nominees by unanimous consent. A fourth nominee was approved by roll call vote.
Carl Tobias, a law professor at the University of Richmond and scholar on the judicial nomination process, said Christensen was a non-controversial choice for the bench as reflected by the unanimous Senate vote.
"He is so well qualified and non-controversial they just agreed without even a roll call vote," Tobias siad.
Tobias taught Christensen at the University of Montana School of Law in the late 1970s.
"He has a great temperament and is a very balanced person,” Tobias said. “He’s very patient. He’s also well-practiced in federal and state courts as civil litigator for his entire career.”
Christensen received his J.D. in 1976 from the University of Montana School of Law and his B.A. in 1973 from Stanford University.