In Portrait of Joseph Leeson, later 1st Earl of Milltown, the subject is depicted in a formal pose, wearing an elegant dark coat with intricate details. The background features a soft, muted landscape that enhances the subject's prominence. Rich colors, particularly deep blues and warm browns, create a sense of depth and sophistication.

The lighting is soft, highlighting the subject's facial features and expression. The painting is executed in oil on canvas, a common medium for portraits of this era, allowing for rich color and detail. Batoni's technique involves smooth brushwork that creates a lifelike representation of the subject. The dimensions are approximately 100 x 130 cm, making it a sizable portrait that commands attention.

The composition is balanced, with the subject positioned centrally against the serene background. Pompeo Batoni was a prominent Italian painter known for his portraits of the aristocracy during the 18th century. This work reflects the Rococo style, characterized by its elegance and decorative qualities. An interesting fact about this portrait is that it was commissioned to celebrate Joseph Leeson's elevation to the peerage, marking a significant moment in his life.

Batoni's ability to capture the personality of his subjects contributed to his popularity among the elite of his time.