The Portugal international headed home an Angel Di Maria cross from the left wing in extra-time to win the match 1-0 at the Mestalla.
It is Madrid’s first Spanish Cup triumph since 1993 and their first major piece of silverware since 2008, and Ronaldo is delighted to have helped the cause.
“It is a great joy to have won and more so that I scored the goal to win the Copa [del Rey],” Ronaldo told reporters after the match. “We had gone many years without winning the cup and we are very happy.
“This is an important trophy and we are enjoying it.”
Ronaldo further praised his compatriot Jose Mourinho, who has won his first major competition as coach of Madrid in his maiden season in Spain.
“Mourinho has made a very positive impact,” said the 26-year-old. “He has helped us a lot and injected us with positive energy, which shows [on the pitch].
"Barcelona played a very good game, but this is the way it goes. The one who scores, wins."
Ronaldo will have another chance to put one over on Barcelona as the nine-time European champions take on their arch-rivals for a place in the Champions League final. The first leg of their semi-final tie takes place at the Bernabeu next week.