In Portrait of Guillaumin, Paul Cézanne captures his friend in a seated position. The painting features a rich palette of greens, blues, and warm earth tones. Guillaumin's face is rendered with a focus on light and shadow, creating depth.

The background is simplified, allowing the figure to stand out prominently. Cézanne's technique is evident in the brushwork, which is both loose and precise. The use of color is striking, with layers of paint that create texture and vibrancy. The composition is balanced, with Guillaumin's figure placed slightly off-center.

This approach is characteristic of Cézanne's style during the Post-Impressionism movement. Paul Cézanne was a pivotal figure in the transition from Impressionism to modern art. This portrait showcases his innovative approach to form and color. Interestingly, Guillaumin was also a painter and a close friend of Cézanne, which adds a personal touch to the work.

The painting reflects the strong influence of light and color that Cézanne would later explore in his landscapes.