Espinosa, 21, will get a $525,000 signing bonus, while Hicks will receive $475,000.
Espinosa is considered an excellent defensive shortstop and not bad with the bat. He hit .309 with four home runs and 37 RBIs as a junior at Long Beach State (Calif.) this season.
Prior to this season, Espinosa was the starting shortstop and won a silver medal for Team USA in the 2007 Pan American Games.
Hicks, 18, is coming off a spectacular career at George Jenkins High School (Fla.), which included a 15-2 record and 0.41 ERA. He also had 155 strikeouts in 119 innings in his final two seasons. The 6-foot-5 left-hander dominated his competition as a senior, going 8-1 with a 0.24 ERA and earning a spot as a FACA Senior All-Star.
Hicks received an All-State honorable mention as a junior, compiling a 9-1 mark with a 0.53 ERA en route to a district title. Hicks led his AAU team to a 2007 national championship in the World Wood Bat Association's 18-and-under division.
To date, the Nationals have agreed to terms with 28 players selected in this year's Draft. It also means they have signed four of their top five picks.
Pitcher Adam Crow, the team's first-round pick, is still unsigned and talks between agent Alan Hendricks and the Nationals are ongoing.
The Nationals feel that Crow's salary should be similar to what pitcher Ross Detwiler received. Detwiler, the team's first-round pick in 2007, received a $2.15 million signing bonus. However, Crow wants a Major League contract and the Nationals are not willing to give it to him. The Nationals have until Friday to get a deal done.
"We continue to have dialog with Alan Hendricks regarding Crow," general manager Jim Bowden said. "But we are not going to give out Major League contracts [to Draft picks]."
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.