He wears a black suit richly embroidered with silver braid, a white lace collar, and matching cuffs, with a black cape draped over his left shoulder. His hair is cut in a straight fringe above the eyebrows, and his pale face is framed by the soft brown locks that fall just above his collar. The boy's expression is calm and composed, his gaze directed outward, engaging the viewer with a sense of quiet authority.

The chair beside him is upholstered in deep red fabric, adorned with gold fringe and large brass tacks, and a matching piece of furniture sits behind him, partially covered by a red cloth. The background is dark and neutral, with a subtle play of light that emphasizes the boy's figure and the luxurious textures of his clothing and surroundings. Velázquez uses fluid, confident brushwork to render the intricate patterns of the embroidery and the sheen of the satin sleeves, while the face and hands are painted with soft, careful modeling.

Touches of gold in the chair and table accents echo the metallic threads in the boy's costume, creating a restrained but harmonious color scheme dominated by black, white, and red. The composition is carefully balanced, with the figure placed slightly off-center and the strong vertical of the chair back anchoring the left side of the scene. A wide-brimmed black hat rests on the red-covered table behind the boy, its brim casting a subtle shadow on the cloth beneath it.

The upper left corner of the painting is filled by a heavy, reddish-brown drapery that falls in soft folds and catches the light along its creases. The floor beneath the boy is painted with loose, broad brushstrokes in warm brown and ochre tones, suggesting a simple, unadorned surface. Light falls most strongly on the boy’s face, hands, and the front of his legs, while the background and corners remain in deep shadow. El príncipe Baltasar Carlos is painted by Diego Velázquez in 1638.