The Yankees got Pineda and pitcher Jose Campos for 22-year- old catcher Jesus Montero and pitcher Hector Noesi, 24.
Pineda, 23, was 9-10 with a 3.74 earned-run average in his rookie season with the Mariners last season. He made 28 starts.
The agreement was reached a week ago, pending the players passing physicals.
To contact the reporter on this story: Eben Novy-Williams in New York at firstname.lastname@example.org
To contact the editor responsible for this story: Michael Sillup at email@example.com