Begonia dregei is a semi-tuberous, fleshy perennial that grows to about 40cm (16 inch) tall, typically with a swollen stem base (caudex). The stem are pale green to reddish green or gray-brown, hairless, branched or branchless. The leaves are small with the blade above green, often with reddish or purplish veins and margins, sometimes white-spotted, especially when young, hairless, beneath paler green, hairless, asymmetric, in outline ovate to ovate-lanceolate, apex acute to shortly acuminate, base deeply to very shallowly cordate or almost truncate, margins entire, toothed or with three to five short or long lobes, the lobes themselves sometimes lobed or toothed, veins palmate. The stipules are persistent, linear-oblong to ovate-oblong.The inflorescence appear in upper leaf axils. It is a few-flowered, bisexual cymose; the flowers are fragrant; the bracts are deciduous, ovate to broadly ovate or oblong. The male flowers are formed by tepals two, white, sometimes pink-tinged or pink, circular or kidney-shaped. The stamens are about 50, arranged in a flattened spherical mass and the anther connectives projecting. The female flowers have bracteoles absent or rarely present and then small and insignificant; the tepals are in number of five, same color as males, ovate, elliptic, almost circular or obovate. The flowers appear in spring and summer. The fruit is three celled capsule, about 1–2cm across the wings.