A muscular, nearly nude man stands in the foreground, his back turned and arm raised as he wields a heavy club against a writhing, many-headed serpent. The monstrous hydra, with scaly green skin and multiple snarling heads, surges from the lower left corner, its open jaws displaying sharp teeth and forked tongues. Each of the hydra’s heads is painted with vivid, ferocious detail, some recoiling as if struck, others lunging forward, their eyes glaring and mouths agape.

The man’s tense muscles and determined expression suggest the immense effort required to battle the creature, while a rough animal pelt is tied around his waist. To the right, a second bare-chested figure emerges from shadow, holding a flaming torch that casts a warm light across the scene. The torch’s flame glows brightly, illuminating the fighters and the hydra’s scaly forms, while the background recedes into deep, smoky darkness.

Light falls most strongly on the central figure’s back and the hydra’s heads, creating dramatic contrasts with the surrounding gloom. The composition draws the viewer’s attention to the violent encounter, with the figures and monster arranged diagonally from the lower left to the upper right. Zurbarán uses bold, energetic brushstrokes for the serpent’s scales and the figures’ skin, while the shadows are rendered in smooth, dark washes.

Small details, like the veins on the man’s arms and the glistening teeth of the hydra, heighten the sense of immediacy and danger. The background is mostly dark and undefined, but a faint suggestion of rocky forms appears behind the figures, rendered in muted browns and grays. A subtle highlight runs along the man's left leg and foot, catching the warm torchlight and emphasizing the contours of his muscles.

In the upper right corner, the darkness is interrupted by a pale, cloudy patch that suggests an opening or mist beyond the cave-like setting. The hydra's lower body coils across the bottom edge of the canvas, its scales shifting from green to ochre as they recede into shadow.