Jenkins, who had worked out for the Cowboys last week, was the 30th overall pick by San Francisco in 2012.
Dallas also Tuesday waived injured receiver Chris Boyd.
Jenkins didn't catch a pass in three regular-season and two playoff games as a rookie for the 49ers. He was traded to Kansas City during training camp in 2013, then had 17 catches for 223 yards and started only three of the 28 regular-season games he played the past two seasons.
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