The silver maple tree is a relatively fast-growing deciduous tree, commonly reaching a height of 15–25 m (49–82 ft), exceptionally 35 m (115 ft). Its spread will generally be 11–15 m (36–49 ft) wide. A 10-year-old sapling will stand about 8 m (26 ft) tall. It is often found along waterways and in wetlands, leading to the colloquial name "water maple". It is a highly adaptable tree, although it has higher sunlight requirements than other maple trees. The leaves are simple and palmately veined, 8–16 cm (3+1⁄4–6+1⁄4 in) long and 6–12 cm (2+1⁄4–4+3⁄4 in) broad, with deep angular notches between the five lobes. The 5–12 cm (2–4+3⁄4 in) long, slender stalks of the leaves mean that even a light breeze can produce a striking effect as the downy silver undersides of the leaves are exposed. The autumn color is less pronounced than in many maples, generally ending up a pale yellow, although some specimens can produce a more brilliant yellow and even orange and red colorations. The tree has a tendency to color and drop its leaves slightly earlier in autumn than other maples.

The flowers are in dense clusters, produced before the leaves in early spring, with the seeds maturing in early summer. The fruit are samaras, each containing a single seed, and winged, in pairs, small (5–10 mm or 0.20–0.39 in in diameter), the wing about 3–5 cm (1+1⁄4–2 in) long. The fruit are the largest among the maples native to its range. Although the wings provide for some transport by air, the fruit are heavy and are also transported by water. Silver maple and its close cousin red maple are the only Acer species which produce their fruit crop in spring instead of fall. The seeds of both trees have no epigeal dormancy and will germinate immediately. Seed production begins at 11 years of age and large crops are produced most years. Like most maples, silver maple can be variably dioecious (separate male or female trees) or monoecious (male and female flowers on the same tree) but dioecious trees are far more common. They can also change sex from year to year.

On mature trunks, the bark is gray and shaggy. On branches and young trunks, the bark is smooth and silvery gray.