The 6-foot-3 switch-hitter will therefore not attend Pepperdine University, where he had already committed. Financial terms have not been disclosed.
Dugan, selected in the second round at No. 75 -- Philadelphia did not have a first-round pick because it signed left fielder Raul Ibanez in the offseason -- hit .379 with eight home runs and 35 RBIs during his senior year at California's Notre Dame High School.
Scouting Director Marti Wolever said on Tuesday that Dugan has a great swing and power from both sides of the plate, predicting that Dugan could average 20-plus homers in his big league prime.
But it was the 18-year-old's mental qualities that caught the organization's attention.
"The makeup is a separator," Wolever said. "This young man's got tremendous makeup, and we've found over the years [that] guys with great makeup really achieve what they're supposed to achieve, and we think he will do that."
For a while, the Phillies were unsure whether Dugan would be available when they were on the clock -- "It was kind of nip and tuck right to the end," Wolever said -- but his selection is emblematic of the club's plan entering the Draft: Choose the best player, regardless of positional need, and improve organizational hitting. The Phillies have a bevy of outfield talent in their Minor League system, but that was not a concern.
"It was the best option for us at this point in time," Wolever said. "He was very high on our board, and we are very pleased to have him."
The Phillies are expected make a formal announcement shortly, once contractual details are finalized and signed.
David Gurian-Peck is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.