A young man stands alone, facing forward, his pale face framed by short, light brown hair and a crisp white ruff that catches the light against his dark attire. He wears a voluminous black cloak over a doublet and breeches, with a gold chain draped diagonally across his chest, its links and pendant rendered in precise, luminous detail. His right hand, emerging from a sleeve with a white cuff, holds a folded white paper or handkerchief; his left hand rests on the hilt of a sword, just above a richly upholstered red chair adorned with gold embroidery.

The background is a muted, shadowy brown, with no architectural setting or landscape, focusing all attention on the figure's solemn presence and stately posture. Light falls from the left, illuminating the sitter's face and hands, and creating subtle highlights on the folds of his black garments, while the rest of his form recedes into deep shadow. The brushwork is smooth and controlled, especially in the rendering of the sitter’s face and the textures of his clothing, with soft transitions in the shadows and crisp edges in the gold chain and ruff.

The composition is vertical and elongated, with the figure nearly filling the height of the canvas, his feet planted firmly on the ground and his gaze directed outward, imparting a sense of authority and reserve. Small details, such as the delicate rendering of the sitter’s ear and the subtle sheen on his shoes, reveal the artist’s close observation and technical skill. The restrained palette of blacks and browns, punctuated by the gold of the chain and the red of the chair, emphasizes the formality and gravity of the king’s presence. The portrait’s scale and composition reinforce the authority of Philip IV, presenting him as both a sovereign and a solitary figure, set apart by the simplicity of his surroundings and the directness of his gaze.