Max Wagner was born in Mexico, the youngest of five boys, to William W. Wagner, a railroad conductor, and Edith Wagner, a writer and correspondent for the Christian Science Monitor during the Mexican Revolution. His father was fatally wounded by Mexican rebels when Max was just 10 years old, and his mother brought him to Salinas, California, where he befriended John Steinbeck, who would later model a character after him in his novel "The Red Pony". Wagner's brothers, Jack, Blake, and Bob, were already working in Hollywood, and Max joined them at 23 years old, securing his first acting part with the help of his brother Jack, who was working on a Harry Langdon film.
Max's early experiences at Mack Sennett honed his talent in physical comedy, which would serve him well throughout his career. He acted in many Spanish-language versions of popular films, often playing supporting roles under the name Max Baron. Studios frequently sought him out to serve as a Spanish-language coach for actors, and he appeared alongside Lupe Velez in the "Mexican Spitfire" series, monitoring her ad-libbing in Spanish to spot any profanity.
Max worked with major studios, but was also a regular with low-budget studio Mascot, appearing in serials such as "The Lost Jungle" (1934) and "The Miracle Rider" (1935). He was a company player with Preston Sturges, appearing in films like "The Palm Beach Story" (1942),"The Miracle of Morgan's Creek" (1944),"The Great Moment" (1944),and "The Sin of Harold Diddlebock" (1946).
During World War II, Max served in the U.S. Army in North Africa. His tough, brawny appearance made him a casting director's perfect choice for gangster roles, giving him unlimited work as a henchman in dozens of Warner Bros. films in the 1930s. He struggled with alcoholism throughout his life, entering Alcoholics Anonymous in 1950 but returning to acting the following year.
Max's most notable appearance in films came in 1953 with the role of Sgt. Rinaldi in the cult sci-fi classic "Invaders from Mars", and he was also cast in "Donovan's Brain", another cult favorite. By the 1960s, Max was cast mostly in bit parts in film and television westerns and dramas, ending his career with small parts in TV series such as "Gunsmoke" and "Columbo".