Jackson gained 149 yards on 22 carries and caught three passes for another 17 yards.
The Rams (1-7) won for the first time since they defeated Dallas just over a year ago.
St. Louis got a touchdown on a fake field goal play, with kicker Josh Brown hitting Daniel Fells on a 36-yard play.
Rams quarterback Marc Bulger completed 17-of-35 passes for 176 yards, with an interception.
Matthew Stafford scored on a 4-yard-run and completed 14-of-33 passes for 168 yards, with an interception, for the Lions (1-6).