Prostanthera suborbicularis is a shrub or undershrub that has its branches and leaves covered with short, matted hairs. The leaves leathery, broadly elliptic to more or less round, in diameter on a petiole up to long. The flowers are arrangedsingly in leaf axils on pedicels up to long, with bracteoles at the base of the sepals. The sepals are almost long with two lobes, the upper lobe about long, the lower about long. The petals are long forming a tube almost long.