Castillo defended his title in a unanimous decision victory over former WBA flyweight champion Eric Morel on March 19, 2005 in Las Vegas, Nevada. Castillo received some exposure in this fight, as it was the first televised bout on the Pay-Per-View (PPV) fight card featuring the first match between boxing superstars Érik Morales and Manny Pacquiao. However, Castillo's victory was a workman-like effort, largely because Morel employed a very defensive style. Castillo followed this victory with another unanimous decision defense of his belt over Hideyasu Ishihara on June 26, 2005 in a fight held in Nagoya, Japan.