[9][10] He was a first cousin of silent film star Emerson Romero, who was a few years older than César and came to New York in 1907 to attend a school for the deaf.

[13] After his parents lost their sugar-import business and suffered losses in the Wall Street crash of 1929, Romero's Hollywood earnings allowed him to support his large family, all of whom followed him to the American West Coast years later.

Romero danced and performed comedy in the 20th Century Fox films he starred in opposite Carmen Miranda and Betty Grable, such as Week-End in Havana and Springtime in the Rockies, in the 1940s.

He also played a minor role as Sinjin, a piano player in Glenn Miller's band, in the 1942 20th Century Fox musical Orchestra Wives.

In The Thin Man (1934), Romero played a villainous supporting role opposite the film's main stars William Powell and Myrna Loy.

Many of Romero's films from this early period saw him cast in small character parts, such as Italian gangsters and East Indian princes.

Romero sometimes played the leading man, for example in Allan Dwan's 15 Maiden Lane (1936) opposite Claire Trevor, as well as winning the key role of the Doc Holliday character (with name changed to "Doc Halliday") in Dwan's acclaimed Wyatt Earp saga Frontier Marshal (1939) starring Randolph Scott and Nancy Kelly three years later.

20th Century Fox, along with mogul Darryl Zanuck, selected Romero to co-star with Tyrone Power in the Technicolor historical epic Captain from Castile (1947), directed by Henry King.

In 1959, Romero was cast as Joaquin in the episode "Caballero" from The Texan,[17] and on September 26 of that year, he hosted the Cuban installment of John Gunther's High Road.

[19] His guest star work in the 1970s included a recurring role on the western comedy Alias Smith and Jones as Señor Armendariz, a Mexican rancher feuding with Patrick McCreedy (Burl Ives), the owner of a ranch on the opposite side of the border.

Arno, a small-time criminal who continually opposes Dexter Riley (played by Kurt Russell) and his schoolmates of Medfield College in a series of films by Walt Disney Productions in the 1970s.

Romero also joined with fellow actors and actresses in lobbying the United States Congress to present the then-dying John Wayne with a Congressional Gold Medal for his service to the nation.

[39] On January 1, 1994, 45 days short of his 87th birthday, Romero died from complications of a blood clot while being treated for bronchitis and pneumonia at Saint John's Health Center in Santa Monica, California.