His first commissions in about 1596 were completed with Giuseppe Valeriano who asked Celio to decorate the Chapel of the Passion in the church of il Gesù in Rome. This work was done after the design of P. Giovanni Battista Fiammeri. He also paints a Madonna and Bambino, now in Santa Maria del Carmine, a The Passage of Moses through the Red Sea (1607) in a vault of the Palazzo Mattei, a Death of the Giants. He painted a St Francis for the altar of the Ospizio at Ponte Sisto. He painted a History of S. Raimondo at the Santa Maria sopra Minerva.
Between 1620 -1638 he helps publish a guide to the churches and artwork in Rome (Memoria delli nomi dell'artefici delle pitture che sono in alcune chiese, facciate e palazzi di Roma). He engraved antique statues. He briefly worked in Parma as a painter for the court of Ranuccio Farnese.
- Works at the Capilla della Passione (1596), iglesia del Gesù, Rome
- Virgin and Child or Madonna (Santa Maria del Carmine)
- The Passage of Moses Through the Red Sea (1607), in the vault of Palazzo Mattei
- Death of the Giants Palazzo Mattei, Rome
- Works at the Capilla Altieri (1622), San Francesco a Ripa, Rome
- Ludovica Albertoni
- Saint Charles Borromeo
- Holy Family and Saint Anne
- St. Francis, an altar of the Ospizio at Ponte Sisto
- History of Saint Raymond, Santa Maria sopra Minerva
- Battle Scene (Borghese Gallery, Rome)
- The History of Painting in Italy from the Period of the Revival of the Fine arts, (1852) by Luigi Lanzi, translated by Thomas Roscoe, page 469)
- (Italian) Cappella della Passione
|Wikimedia Commons has media related to Gaspare Celio.|
- Sydney Joseph Freedberg (1978). Paintings in Italy, 1500-1600
- The Grove Dictionary of Art, MacMillan Publishers (2000)
- José Luis Colomer, Arte y diplomacia de la monarquía hispánica en el siglo XVII (Art and Diplomacy in the Spanish Monarchy in the 17th Century), CEEH (2003). ISBN 84-933403-0-8
- Comune di Bozzolo; Gruppo Culturale Per Bozzolo (a cura di), Il Principe e la Città. Giulio Cesare Gonzaga di Bozzolo, Modena, 1994. ISBN non esistente.