Andreotti was born in Florence. He initially studied at the Florentine Academy of Fine Arts. A few years after entering the Academy, sixteen-year-old Andreotti won a stipend and ultimately gained an appointment as a professor at the Academy. He was a prolific painter of canvases, first dedicating himself to fresco painting. Then, he began to gain a growing reputation for depicting decorative pictures that a new and constantly expanding group of international collectors found so appealing in Rome, Florence, and other cities.
His academic studies prepared him well for his chosen subject - historical figurative works set in the 16th and 17th centuries. Andreotti's paintings were sought after by American and European collectors alike, and during the late 19th century, he received an important commission from the King of Italy.
Andreotti combined his technical precision, learned in his anatomy classes at the Academy, with the new theories on color and technique explored by the Impressionists. His paintings often feature significant figures created with a colorful palette and open brush strokes while keeping true to the academic traditions of anatomical correctness.