The Patriots and McDonald, who played at South Carolina State, have been linked since May. At 6-foot-3 and 190 pounds, McDonald is a taller receiver who totaled 159 catches for 2,389 yards and 17 touchdowns over his college career.
Meanwhile, Maine receiver Derrick Johnson, who was with the team for a few weeks in May, will also be re-signed, according to a source. News of Johnson's return was first tweeted by Jeff Howe of the Boston Herald.
As Mike Lowe of the Portland Press Herald in Maine reported in June, Johnson was a candidate to return to the Patriots after he recovered from a sprained knee.
The Patriots are well-stocked at receiver, and if McDonald and Derrick Johnson ultimately stick with the team, the practice squad is the most likely spot.
With the additions of McDonald and Johnson, the Patriots will have 89 players on their 90-man roster.