At the centre of the composition, the Virgin Mary sits enthroned, draped in vivid blue and red, holding the Christ Child on her lap. The Christ Child leans forward, grasping the hand of a kneeling young woman in a golden gown, who offers her left hand for a ring, enacting the mystic marriage of Saint Catherine of Alexandria. To Mary's right, a bearded man in a brown robe stands close behind her, while to her left, another male saint in yellow and red holds a sword upright, gazing thoughtfully at the scene.

Above, two cherubs hover in the air, one holding a garland of flowers, their forms illuminated by a shaft of light that falls diagonally across the upper half of the painting. A dramatic red drapery sweeps behind the Virgin and Child, framing the upper group and intensifying the sense of grandeur. On the right, a muscular, wild-haired figure in a rough garment gestures energetically, while two small children, one holding a lamb, stand at his feet on the steps.

The lower half of the painting is crowded with saints and figures in varied poses: a bishop in golden vestments kneels in prayer, his crozier raised, while beside him a monk in black bends forward, hands clasped. To the left, a knight in gleaming armour stands with one foot on a defeated dragon, his gaze turned toward a youthful, nearly nude male figure who holds a palm frond and looks upward. A group of women and a nun cluster at the far left, one holding a set of scales, another with her hands clasped, all eyes fixed on the Virgin and Child above.

The architectural setting is grand, with monumental columns and steps leading up to the throne, rendered in cool greys and ochres that contrast with the rich colours of the figures' garments. Rubens uses sweeping, fluid brushstrokes to model flesh and drapery, creating a sense of movement and vitality throughout the crowded scene. The composition is carefully orchestrated, with diagonals formed by the gestures and gazes of the figures, guiding attention toward the central act of the mystic marriage. The museum describes the subject as the mystic marriage of Saint Catherine of Alexandria before the Madonna and Child, surrounded by saints.