Born in the province of Vicenza in northern Italy, Matteo Sandonà immigrated to the United States in 1891. The young Sandonà expressed an interest in and talent for drawing, and, in 1896, his father sent him back to Italy, where he enrolled at the L’Accademia di Pittura e Scultura di Verona, now called Accademia Cignaroli. One of his teachers there was the renowned realist artist Mosè Bianchi (1840–1904). In Venice, Sandonà likely saw the work of Giovanni Boldini (1842–1931) and John Singer Sargent (1856–1925), both consummate portrait painters. Returning to the United States in 1900, Sandonà furthered his education with classes at the National Academy of Design in New York. In 1901, he moved to San Francisco where he became associated with artists Xavier Martinez (1869–1942), Gottardo Piazzoni (1872–1945), and Charles Peter Neilson (1867–1937). In 1902, they and other progressive artists founded the California Society of Artists, which stood in opposition to the more conservative San Francisco Art Association.
Sandonà established his reputation as a portrait artist, painting in the modern bravura style inspired by Boldini and Sargent. He received commissions from notable people from San Francisco to Los Angeles, among them actress Mary Pickford and soprano Dame Nellie Melba. In 1903, he made the first of several trips to Hawai’i, having been commissioned by prominent families there, among them Sanford B. Dole, first territorial governor (1900–1903) and Anna Rice Cooke, founder of the Honolulu Academy of Arts. After losing his studio during the 1906 earthquake and fire, Sandonà went to Europe for a year. Upon his return, he became active again in the San Francisco art scene, including the San Francisco Art Association. In 1915, he served on the International Jury of Awards at the Panama-Pacific International Exposition in San Francisco.