A mixed material frame is a load-bearing skeletal structure composed of multiple different materials each contributing to form a stable structure by counteracting gravity, wind, seismic movements, and any other forces acting on the framework.

Usually each material in a mixed frame plays a distinct role, with the different materials complementing each other's strengths. Normally one of the materials performs best at resisting compression (e.g. concrete or masonry) while the other material is best at maintaining tension across a long span or a great height (e.g. steel or wood).

When adjoining parts of a structure (such as a sideways addition) are made of different single materials, then the building is not classified as mixed material.