An arrest warrant for first-degree murder has been issued for Henry John Peter.
Last week, police arrested Dennis Henry Hahn and charged him with first-degree murder as well.
Police allege two masked men broke into the home of Frances Wendland in Rosthern in December 1985.
The locked her two daughters and a friend who had been sleeping over in a basement bathroom.
When the girls escaped a couple of hours later, they found Wendland dead in a bedroom.
A previous trial heard she had been tied with packing tape and her neck and mouth were tightly bound. Pathologists testified she died from neck compression.
A jury convicted Donald Marlow of first-degree murder for being an accessory to the killing. Court heard Wendland's estranged husband, Larry, used Marlow to hire two men to kill her.
Larry Wendland, who married the couple's babysitter a year after the killing, committed suicide in 1989.
Hahn was arrested in Surrey, B.C., and is to appear in Saskatoon court on July 27.
Mounties say anyone with information about Peter should call the RCMP's historical case unit or Crime Stoppers.