Thome is hitting .242/.338/.516 this season with five home runs and 15 RBIs.
Thome owns a career batting line of .277/.402/.556 and has hit 609 home runs, tied for seventh all-time.
"Jim Thome is a real pro, and he specializes in hitting home runs and getting on base, and he's done that his whole career," Duquette said. "Beyond that he's a terrific teammate and a steady presence and he's a veteran, he's been around."
Duquette said the move was made to add more depth to a lineup that has left-handed hitters Nick Johnson, Nick Markakis and Endy Chavez on the disabled list.
With Nolan Reimold likely out for the remainder of the season after undergoing surgery on his neck Monday, Duquette also wanted to add some pop to the lineup.
"We had to look at adding power to our team, and also we have a real strong lineup versus left-handed pitching and I think that this will give us a stronger lineup, particularly versus right-handed pitching," Duquette said.
Lino, a 19-year-old catcher from Venezuela, is rated the Orioles 11th-best prospect by MLB.com and was hitting .218 with four home runs and 18 RBIs with Class A Delmarva.
Simon, a 21-year-old right-hander who was a fourth-round pick out of the University of Arizona in the 2011 Draft, is 2-8 with a 3.96 ERA with Class A Frederick. He is rated the Orioles' 20th-best prospect by MLB.com.
"We like both of the young players," Duquette said. "We thought that Thome's presence and our need for the Major League team were worth the value that we have to give up in a trade."
The Orioles designated left-handed pitcher Zach Phillips for assignment to make room for Thome on the 40-man roster. If Thome is to be activated Sunday, the Orioles also will need to create space on the 25-man roster, although no move has been announced.
Thome has 18 home runs and 45 RBIs in 67 career games at Camden Yards. In a three-game series in Baltimore on June 8-10, Thome was 6-for-13 with a homer, two doubles and four RBIs.
"No ballpark can hold that guy," said Orioles first-base coach Wayne Kirby, who played with Thome in Cleveland from 1991-96. "His power, his ability to adjust, his ability to hit. By all means, he's not an easy out. He's not an easy out at all."
Thome has been to the playoffs nine times -- including two World Series runs -- an experience Duquette said was an attractive asset for a team in the midst of a streak of 14 consecutive losing seasons.
"Goes about the game the right way," Kirby said. "Professional. Treats everyone with respect, and he will help you."
Phillies general manager Ruben Amaro Jr. said he started receiving calls from American League teams about Thome's availability after the 41-year-old slugger hit four home runs and 14 RBIs in nine Interleague games as the team's designated hitter.
Thome played first base for four games in April before a back injury sent him to the disabled list, raising doubts about whether he will ever be healthy enough to play first base again.
"Well, he's been hitting, and that's his primary asset," Duquette said when asked about the injury. "He should be able to hit."
With first baseman Ryan Howard on the mend and no designated hitter in the National League, speculation on Thome joining an American League club had been rampant. Duquette said the move had been in the works for about a week prior to Saturday.
"We're going to welcome him with open arms," Chris Davis said, "and hopefully he can swing it for us like he can against us."
The Orioles have used eight different players at designated hitter this season, with Davis and Johnson leading the way with 19 starts each.
Johnson was placed on the 15-day disabled list Thursday because of a right wrist injury, while Davis has been playing in right field in place of injured starter Markakis, who has been on the disabled list since having a piece of his broken right hamate bone removed on June 1.
Thome did not play during the Phillies' 3-2 loss to the Marlins on Saturday.