Sanchez, 6-foot-1, 205 pounds, was the Mariners' top-rated international prospect, according to Bob Engle, the team's vice president of international operations.
"He is a very strong and sturdy built young man, who has sound pitching mechanics and a quick arm," Engle said. "He is a power pitcher with above-average arm strength and has a chance to have a power curveball. Sanchez is a very good all-around athlete and is extremely poised for a 16-year old."
Leal is a 6-3, 215-pound right-handed hitter.
"Jose is a big, strong, raw-boned player who has the potential to be an above-average Major League player," Engle said. "We feel he has the ability to hit, and hit with power. He is a hard worker and has a great mental approach to the game."
The two youngsters were at Safeco Field on Tuesday, checking out the facilities before signing their contracts.
"We are extremely pleased that both players have decided to sign with our organization," Engle said.