The 21-year-old from Milford, Ohio, had a slash line of .336/.392/.618 with 15 home runs and 67 RBIs this season with the Wildcats.
If Mahan pans out, he could become the second University of Kentucky player to make an impact for the Marlins in recent years. In the 13th round in 2013, Miami selected JT Riddle, who is the club's everyday shortstop.
Marlins vice president of scouting Stan Meek said the team is looking for up-the-middle depth, which is one reason left-handed-hitting center fielder Brian Miller was selected in Competitive Balance Round A on Monday.
The Draft concludes on Wednesday, with exclusive coverage of Rounds 11-40 beginning on MLB.com at noon ET.
Round 4: RHP Colton Hock, Stanford
After selecting three straight position players in the 2017 MLB Draft, the Marlins went with Stanford right-hander Colton Hock in the fourth round Tuesday.
A reliever during his college career, Hock could get a shot at becoming a starter. An imposing 6-foot-4, 220 pounds, the right-hander saved 16 games this season.
Hock is from Bloomsburg, Pa., and the 21-year-old was 6-1 with a 2.08 ERA, striking out 35 in 47 2/3 innings. The Marlins are targeting strike-throwers, and Hock walked just 11.
Round 5: RHP Ryan Lillie, University of California-Riverside
Troy Percival, the closer on the Angels' 2002 World Series champion team, made the switch from catcher to reliever. Now the head coach at the University of California-Riverside, Percival initiated the change for Ryan Lillie.
A converted catcher, Lillie is now a right-handed pitcher, and the Marlins are hopeful he can someday mirror the success of his college coach. Miami selected Lillie in the fifth round on Tuesday.
In his UC-Riverside career, Lillie enjoyed success as a closer and showed potential when given a chance to start. The right-hander's fastball is in the 92-95 mph range, and he's touched 97 mph.
Primarily a strike-thrower, Lillie had a 4.69 ERA in 20 games (10 starts). He struck out 80 and walked 20 in 71 innings.
Round 6: RHP Taylor Braley, University of Southern Mississippi
The Marlins added versatility and intrigue when they selected University of Southern Mississippi right-hander Taylor Braley in the sixth round.
Named first-team All-Conference USA as a utility player, Braley is the epitome of an all-around player. He was impactful on the mound -- possessing a 93-mph fastball -- and he was a power threat at the plate, belting 17 home runs.
Braley gives the club options. As a pitcher, he was 7-2 with a 3.40 ERA in 14 games (13 starts). The right-hander struck out 78 in 82 innings, and he walked just 22.
But Braley also stood out hitting, with a slash line of .313/.461/.587 with 17 home runs and 61 RBIs. He set a school record with 59 walks, showing tremendous plate discipline.
Round 7: LHP Sean Guenther, University of Notre Dame
Left-handed relievers are hard to come by, and the Marlins may have found an option who can move through their system quickly. In the seventh round Tuesday, Miami selected Sean Guenther from the University of Notre Dame.
Guenther's fastball sits in the 90-93-mph range, but he has an advanced slider, which could make him a candidate to move up the Minor League ranks quickly.
A native of Atlanta, Guenther posted a 2.64 ERA this year in 24 appearances, picking up seven saves, and he struck out 69 in 58 innings. His slider is his swing-and-miss pitch.
Like most of the pitchers the Marlins have taken this year, Guenther is a strike-thrower, having walked just 19.
Round 8: C Jared Barnes, University of South Alabama
The Marlins traditionally have made a practice of picking at least one catcher in the first 10 rounds. Jared Barnes became the choice on Tuesday in the eighth round.
From Tallahassee, Fla., Barnes attended the University of South Alabama. His season was cut short in May due to a finger injury.
At this stage of his development, Barnes is advanced defensively, especially with his receiving skills. The question is whether he will hit enough to become an big league regular.
For the Jaguars, Barnes had a slash line of .320/.416/.605 with 13 home runs and 50 RBIs.
Round 9: CF Cameron Baranek, Hope International University
The Marlins continue to build outfield depth, and they may have uncovered a talent from a small NAIA school in Fullerton, Calif.
In the ninth round Tuesday, Miami selected center fielder Cameron Baranek from Hope International University.
Baranek initially had an opportunity at the University of California-Irvine, but he ended up at Hope International, where he was an NAIA All-American honorable mention.
Baranek posted impressive numbers, with a .364/.486/.672 slash line, 14 home runs and 40 RBIs. He added 13 doubles, three triples and stole 20 bases in 30 attempts.
Round 10: 3B Denis Karas, UC-Berkeley
All eight of the Marlins' picks on Day 2 of the Draft were college players. In the 10th round, Miami went with Denis Karas, a third baseman from the University of California-Berkeley.
The junior appeared in all 54 games, and his 12 home runs were tied for the most in the Pac-12.
Karas is an athletic infielder who can also play first base. Along with his 12 homers, he added 11 doubles, scored 28 runs and drove in 37.
Joe Frisaro has covered the Marlins for MLB.com since 2002. Follow him on Twitter @JoeFrisaro and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.