- Bishop of Salamanca (1339-1361), and Bishop of Segovia (1361-1362).
- Participated in the siege of Algeciras (1342)
- Together with Sáncho Blázquez Dávila, Bishop of Ávila, he agreed that King Pedro I of Castile could marry Juana de Castro, despite his recent marriage to Blanche of Bourbon and living openly with his mistress María de Padilla.
- Officiated at the marriage between Pedro I of Castile and Juana de Castro, in the church of St. Martin of Cuéllar. Juan Lucero may have been coerced by the fear of the monarch's rage, though incurring the wrath of the papal legate .