Having moved to Spain in his teens after being born in Chiclayo, Lambayeque Region, Merino played youth football with FC Barcelona (only one year) and RCD Mallorca.

In January 2003, Merino joined Atlético Malagueño, being an important midfielder element as Málaga CF's B-team retained their newly acquired status in Segunda División, with the player having contributed with 20 games and five goals to the promotion (play-offs included).

[1] Subsequently, he moved to Switzerland and signed with Servette FC but, with the club facing bankruptcy, left in the following transfer window to Ciudad de Murcia – also in Spain's second level – alongside teammate João Paulo Daniel.

[5] On 28 February 2011, Merino signed a half-season contract with Unión Comercio[6]– at almost 29, this marked the first time he would be playing in the Peruvian Primera División.

He decided to play for Peru as a senior, earning his first and only cap on 7 June 2009 in a 1–2 home loss against Ecuador for the 2010 FIFA World Cup qualifiers.