Born in Rome in 1654, he studied with Carlo Maratta, learning a classical and academic style, in line with the dominant taste in Rome at that time. Chiari soon earned considerable success among his contemporaries. 

In 1697, he was admitted to the San Luca Academy and, subsequently, his prestige led him to become the Prince, or First Director of this institution. 

Chiari reached the peak of his fame during the pontificate of Clement XI Albani (1700 - 1721), a cultured man, patron and supporter of numerous artists. The Pope summoned the best living talents to carry out a great project for the architectural and artistic renewal of the city of Rome. Pope Albani commissioned Chiari, together with his master, to produce numerous paintings for the Basilica of Saint Peter, Saint Giovanni in Laterano and the Church of the Holy Apostles. 

Important commissions also arrived from numerous aristocratic Roman families, including the Colonna, the Barberini, the Spada and the De Carolis. 

In his artworks, Chiari was often inspired by the greatest exponents of seventeenth-century classicism, such as Andrea Sacchi and Guido Reni, as well as Baroque masters, especially Pietro da Cortona. 

His later work was the most original, both in terms of large Baroque decorations and easel paintings. His style became softer and brighter, characterized by a range of clear colours, rich in nuances. 

Chiari died in Rome in 1727, where he was buried in the Church of Saint Susanna.