The Mets claimed Castillo off waivers from Arizona on Friday, Will Sammon of The Athletic reports.
Castillo was designated for assignment in December after Lourdes Gurriel re-signed with the D-backs, and Castillo will now move across the country to join New York. The 26-year-old made just one plate appearance in the majors last year while slashing .313/.431/.410 with 72 RBI in Triple-A. He'll likely begin the year at Triple-A Syracuse.