The former Olympiakos and Manchester City striker will return to the Concacaf nation after spending 12 years in Europea
After 12 years in Europe, the 28-year-old celebrated his most recent birthday by leaving Aris Thessaloniki and signing a three-year contract with the Hidalgo side.
Castillo will reunite with Hugo Sanchez, who coached him from 2007 to 2008 with El Tri. The former Olympiakos striker burst onto the international scene under Sanchez's tutelage, with a fantastic Copa America 2007 campaign that saw Castillo score against Brazil, Ecuador and Paraguay.
His performance at the South American competition sealed a big-money transfer to Shakhtar Donetsk, but he struggled to nail down a first-team spot. Loan spells at Manchester City, Dnipro Dnipropetrovsk and Chicago Fire failed to deliver the striker back to his best form.
A return to Greece with Aris stabilised his career and prompted media talk that he may be recalled to the national side after a long absence.
In recent years, Chivas and Cruz Azul had been named as suitors for Castillo, but it is believed that the player had turned them down in an effort to remain in Europe.