Little is known about the life of Juan del Castillo, one of Seville's leading painters of the 1630s and 1640s. Documents establish the boundaries of his career as 1611 and 1650. Scholars also know that he was related by marriage to painter Alonso Cano, his Sevillan peer, and to Bartolomé Esteban Murillo, who became Castillo's apprentice. His Sevillan predecessors influenced Castillo's warm palette. The naturalism that distinguished his manner derived from the Venetian paintings that were relatively abundant in Seville.
Castillo's most important commission was a series of paintings for the altarpiece of a convent in Seville, beginning in 1636. Taddeo Zuccaro's painting of the same subject inspired his composition for the central panel of the Assumption of the Virgin, but Castillo derived the movement and theatricality of some figures from Peter Paul Rubens's style. Castillo's carefully painted landscape backgrounds establish him as one of Seville's key contributors to that tradition during the 1600s. He influenced the highly renowned Bartolomé Estebán Murillo in both naturalism and figure style.