The Spanish football federation says the two clubs agreed to play the April 20 match at the 52,000-capacity stadium.
Barcelona won the last meeting against Madrid in 1990, which also came at the Mestalla, 2-0.
The Mestalla has hosted eight finals, including Barcelona’s 4-1 win over Athletic Bilbao in 2009 for its record 25th triumph.
Barcelona plays at Real Madrid in the league four days prior to the final. Two-time defending league champion Barcelona holds a seven point lead over Madrid in the standings.
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