His grandfather's master King John III of Portugal sent the young painter to study with Anthonis Mor (also known as Antonio Moro) in Flanders around 1550.

The painter spent the remainder of his life at the court, becoming a personal favourite of the king and acquiring honours and wealth.

Although influenced by the paintings of both Mor and Titian, these portraits display an original talent and reflect admirably the modesty and formality of the Spanish court.

The double portrait of the Infantas Isabella Clara Eugenia and Catalina Micaela (1568–9; Madrid, Convent of Las Descalzas Reales) is an example.

[1] Coello was a follower of Titian, and, like him, excelled in portraits and single figures, elaborating the textures of his armours, draperies, and such accessories in a manner that had a notable influence on Velázquez's style regarding those objects.

[3] From Mor, Coello learned precision in representation, and from Titian he incorporated Venetian gold tones, generous workmanship, and the use of light on a canvas.

[4] While his debt to Mor is evident, Coello brought distinctive qualities to the court portrait, notably a sharp sense of colour, a crispness of execution and a heightened realism.

The religious works, many of which were created for El Escorial, are considered good but undistinguished examples of the more conventional austere style.