Dunn, who opened the season on the disabled list with a left forearm strain, will throw 15 pitches (all fastballs) on Tuesday. If the bullpen session goes well, the southpaw will be back on the mound Saturday.
"He's progressing," manager Don Mattingly said of Dunn. "We're happy with what's going on with him. We're happy with his progression."
Dunn has been throwing off flat ground in recent weeks without any discomfort. On Tuesday, he will pitch off the mound for the first time since early April. As his progression continues, Dunn will move closer to pitching in at least one rehab assignment with Class A Jupiter in the Florida State League.
Jackson, who has been on the disabled list since April 19 with a right triceps strain, has pitched off the mound twice since landing on the DL.
"He's going to throw a [simulated] game on Wednesday," Mattingly said. "He's going to face a couple of hitters."
Jackson has made four relief appearances this season and has a 2.45 ERA in 3 2/3 innings.
Before both return to the Marlins, they will pitch in at least one Minor League rehab game, meaning they are at least a couple of weeks away from activation.
Worth noting: The Marlins have a doubleheader scheduled for Saturday on the road against the Nationals, making up the postponed April 9 game. Justin Nicolino will start one of those games, but it hasn't been determined which game he'll be on the mound for. Mattingly said the team is expected to promote another starter from the Minor Leagues to start the other game.