Mimosa is a small tree with widely spreading branches, a short trunk, and a broad, flat-topped crown.
Leaves are alternate, twice-pinnately compound (fernlike), 6–20 inches long, the pinnae (first division) branches 2–6 inches long, the leaflets about ½ inch long, lacking teeth but with hairs along the edges. Leaves emerge in spring.
Bark is smooth, tight, blotched gray and sometimes brownish on young growth; pores large and conspicuous.
Twigs are moderately stout, green to brown or gray, somewhat fluted below nodes (where leaves attach), often zigzag, smooth; pores small, numerous.
Flowers May–August (after leaves emerge), on tips of branches, pink, crowded in tassel-like round heads, 1½ inches across; fragrance is strong and sweet.
Fruits August–September; pods are flat, linear, yellowish-brown, 5–8 inches long, forming large clusters; seeds are flat, light brown, oval, about ½ inch long.