Michael Conrad, the actor who won two Emmys for his portrayal of the tough, paternal Sgt. Phillip Esterhaus on the television police drama ''Hill Street Blues,'' died of cancer yesterday in Los Angeles. He was 58 years old.

Over the years, Mr. Conrad gained a wide variety of movie and television credits, but he may be best remembered for his role as the Hill Street police sergeant who ended his morning briefing by warning fellow officers, ''Let's be careful out there.''

According to NBC, Mr. Conrad was born in New York City and, after serving in the United States Army field artillery, attended City College. He later studied drama in a number of workshops and toured with productions of ''A Streetcar Named Desire,'' and ''Mr. Roberts.'' He also made one-time appearances on several television series and played a regular part on the soap opera ''The Edge of Night.''

Mr. Conrad moved to Hollywood in 1963 and appeared in a number of motion pictures, including ''They Shoot Horses, Don't They?'' ''Castle Keep,'' and ''The Longest Yard,'' in which he played the coach of a football team of prison inmates.

But he did not secure a regular major role in a television series until 1976, when he co-starred with Judd Hirsch in a police drama entitled ''Delvecchio.'' The show lasted one season.

Mr. Conrad played the role as the aging Sgt. Esterhaus for four seasons, and this year taped 10 of the show's 22 segments. Of the character, Mr. Conrad once remarked, ''He's a cop who has been out on the street too many years and was burned out.''

He is survived by his fourth wife, Sima.