Gilbert, 48, is best known for her work on TV's "Little House on the Prairie." She also recently competed on "Dancing with the Stars."
Busfield, 55, is a former cast member of the small-screen dramas "Thirtysomething," "The West Wing" and "Studio 60 on the Sunset Strip."
"They are engaged and both are incredibly happy," Gilbert's representative told People.com.
An insider told the celebrity magazine the couple got engaged during the holidays.
The report did not say where or when the pair intend to wed.
Gilbert was previously married to actors Bo Brinkman and Bruce Boxleitner.
Busfield has also been married twice.