In 1966, after several years away from public service, Jensen ran successfully for the District 17 state senate seat being vacated by
John M. Zwach, Sr., who was running for the
U.S. Congress. District 17 later became District 28 after
redistricting in 1970, and included all or portions of
Brown,
Cottonwood,
Murray,
Nicollet and
Redwood counties. He was re-elected in 1970, 1972 and 1976. As representative and senator, Jensen allied with the House Conservative Caucus at a time when the legislature was still officially
nonpartisan. He later identified as
Republican when major party affiliation became common. His key areas of interest were agriculture, commerce, the judiciary, and taxes and tax laws. While in the senate, Jensen served on the Commerce, Elections, Environment & Natural Resources, General Legislation, Health, Welfare & Corrections, Judiciary, Public Highways, Rules & Administration, and Taxes & Tax Laws committees, and on various other committee incarnations and subcommittees. He was chair of the General Legislation Committee from 1971 to 1973, and was an
assistant minority leader from 1977 to 1981. He also served on the Minnesota
Voyageurs National Park Commission during the 1970s. Jensen did not to run for re-election in 1980, as he was appointed to the Minnesota Tax Court by
Minnesota Governor Albert Quie. He served on the tax court from 1981 to 1986. In 1986, he ran unsuccessfully as a
Minnesota Democratic-Farmer-Labor Party candidate for the Minnesota Senate.{{cite web|url= http://www.leg.mn/archive/LegDB/Articles/10281STParty.pdf |title = Carl Jensen may quit |publisher = Star Tribune (Minneapolis, MN)|date= July 10, 1986 ==Personal life==