Vieja hartwegi is a large, robust cichlid known for its striking coloration and elongated body. Adults typically display a blue-gray to greenish body with a distinct reddish or orange head, particularly pronounced in dominant males or during breeding. The dorsal and anal fins are elongated, and males are more colorful and larger than females.

Adult size can reach 25–30 cm, making them suitable for spacious aquariums or biotope setups.