Initially constructed in 1858 to a design by architect Alfred Price, with extensive interior and facade remodelling dating from 1937 designed by La Poer Terry, is of Regional historic, technical and architectural significance.
Historically, the shell of the Theatre Royal is one of the oldest theatre remnants in Australia. As a combination of hotel and theatre, it was an important social gathering point in early Castlemaine, which was an early focus of the Victorian goldfields. As a properly equipped theatre and later as a permanent cinema, the Theatre Royal catered to the citizens of the Castlemaine district with plays, concerts, recitals and events in the 19th century, and all the various developments of film, from "light shows" and bioscopes through to modern cinema, its mainstay in the 20th.
Technically, the roof is significant for being clad with Morewood and Rogers patent iron tiles, possibly the largest roof expanse still existing of these tiles.
Architecturally, the interior is a fine example of the Moderne (Art Deco) style, commonly found in cinema buildings of the 1930s, with decorative plasterwork in the auditorium.