The 6-foot, 185-pound Andrade was one of the top players on the Venezuelan team that won the 15-and-under world championship in Mexico last August.
The international signing period opened Tuesday and many of the top youngsters have agreed to contracts, with Seattle also reportedly in agreement on a $350,000 contract with 16-year-old outfielder Ronald Rosario from the Dominican Republic.
Rosario is a 6-foot-2, 165-pound left-hander from San Cristobal who is projected as either an outfielder or pitcher.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.