A group of seven men in dark clothing and white ruffs gathers closely around a pale, lifeless body stretched out on a wooden table. At the right, a man in a black hat and lace collar, identified as Nicolaes Tulp, sits slightly apart and demonstrates the anatomy of the left forearm, lifting tendons with a pair of forceps as he gestures with his free hand. The corpse lies supine, its torso and limbs exposed to the light, with the muscles of the left arm carefully revealed in red and pink tones, while the face is turned toward the viewer, eyes closed and mouth slightly open.

The other figures lean in, watching intently; some gaze at Tulp, others at the dissected arm, their faces animated by curiosity or concentration. Behind the group, a large anatomical textbook lies open on a stand at the lower right, its pages illuminated and its text rendered in careful detail. The background is subdued, with a shadowy architectural setting and a faintly visible arch, focusing attention on the figures and the dramatic play of light across their faces and the body.

Rembrandt arranges the composition in a tight, pyramidal cluster, using strong contrasts of light and shadow to model forms and create a sense of immediacy. The brushwork is smooth and precise, especially in the rendering of flesh, fabric, and facial hair, while the color palette is dominated by blacks, whites, and flesh tones, punctuated by the vivid red of the exposed muscles. At the upper left, Rembrandt signs and dates the painting, using his forename in its original form, Rembrant, followed by 'fecit 1632.' Rembrandt transforms the traditional group portrait by placing the corpse at the center and staging the lesson as a dramatic scene, rather than a static record. The painting is now regarded as one of Rembrandt's early masterpieces and is a key work of the Dutch Golden Age painting movement.