Dunning received a $2 million signing bonus, according to a club source, which is just below slot value for the 29th selection in this year's draft.
A 6-foot-4 right-hander from the University of Florida, Dunning held off signing until now in part because he was still pitching for the Gators in the College World Series. He went 6-3 with a 2.29 ERA, 88 strikeouts and 12 walks in 33 games (28 of those out of the bullpen); the Nats plan to use him as a starter once he begins pitching in their farm system.
Dunning joins fellow first-round pick Carter Kieboom (selected just above him at No. 28) as the two newest front-end prospects in the organization. Kieboom, a high school shortstop from Georgia, signed shortly after last month's draft, also for $2 million.
The Nationals also announced the signing of 12th-round pick Hayden Howard, a left-hander from Texas Tech. That means all of their top 19 picks in the year's draft have come to terms.