The façade of the Sibelius Museum consists of industrially cast concrete panels. The relief-like pattern of the façade is created by the shuttering panels used in casting, placed at right angles to each other in different patterns. The façade alongside the main entrance features a strip window with concrete frames, possibly inspired by Le Corbusier.

The main entrance is characterised by large windows and glass doors with brass-coloured handles in a bark pattern. There are three large glass doors on the river side too. In some places, the façade is almost entirely glazed. Worn concrete elements were replaced and new windows installed when the frontage was renovated in 2010–2011.