A man with a lined face and a prominent nose appears in profile, facing left, his features quickly suggested with dark, fluid lines. He wears a broad, flat cap that sits low on his head, its brim rendered with sweeping strokes that give it a sense of weight and texture. The background is left plain, focusing all attention on the figure and the expressive quality of the ink work.

The drawing is executed with swift, confident strokes, some lines thick and assertive, others light and almost transparent, creating a vivid sense of immediacy and movement. Details such as the man's ear, the outline of his jaw, and the creases in his clothing are suggested rather than fully described, leaving much to the viewer's imagination. A small mark or inscription appears in the upper right corner of the sheet.

No secondary figures or objects are present in the composition, leaving the man isolated against the blank background. The background is a uniform, unadorned beige tone, with no indication of setting or environment. The ink varies in saturation, with some lines appearing almost black and others fading to a lighter brown.

The handling of the pen is especially loose in the depiction of the garment, where looping, overlapping lines suggest folds without precise definition. Edges of the drawing are uneven, with several lines trailing off toward the margins and leaving open spaces around the figure. Bust of an Elderly Man in a Flat Cap is by Rembrandt and dates to 1635. The museum lists pen and brown ink as the materials used for this drawing.