Mercati is known for a precise etching style that balances religious narrative with architectural accuracy. In works like "The Marriage of Saint Catherine" or "The Baptism of Christ", he uses clear lines and structured compositions. He frequently incorporated large stone blocks or tablets into his frontispieces to frame titles and dedications. This technique gives his prints a sense of permanence. His figures often possess a calm dignity that contrasts with the energy of some Baroque contemporaries.

Modern collectors value Mercati for his ability to bridge the gap between fine art and historical documentation. His views of Rome, such as "Sta. Agnese", are windows into a lost version of the city. These prints offer a sophisticated aesthetic for contemporary interiors. The monochrome palette of his etchings allows the structural details to remain the primary focus. They provide a sense of historical continuity and classical balance in a modern room.