A curved sign assembly includes a flexible sign panel removably mounted in an arcuate position in a modular frame. The frame comprises a pair of edge rails mounted on opposite side edges of an intermediate member. The edge rails can clip on a variety of intermediate members of different sizes. The edge rails include inwardly facing open-sided channels that receive and hold side edges of the flexible sign panels on one or both sides of the intermediate members. Upper and lower plates cover the top and bottom sides of the sign. Horizontal or vertical reinforcing members positioned on the intermediate member for larger signs support the sign panels between the edges. The edge rails can be decorative extruded aluminum members that are attached in different lengths to a variety of intermediate members. A channel member can be mounted between the edge rails to receive the ends of sign panels that extend only part of the way between the edge rails and the side of the intermediate member.