<b><i>Introduction:</i></b> The <i>GNB1</i> (guanine nucleotide-binding protein, β1) gene encodes for the ubiquitous β1 subunit of heterotrimeric G proteins, which are associated with G-protein-coupled receptors (GPCRs). <i>GNB1</i> mutations cause a neurodevelopmental disorder characterized by a broad clinical spectrum. A novel variant has recently been confirmed in a case of rod-cone dystrophy. <b><i>Case Presentation:</i></b> We describe the second confirmed case of a classical rod-cone dystrophy associated with a mutation located in exon 6 of <i>GNB1</i> [NM_002074.5:c.217G&gt;C, p.(Ala73Pro)] in a 56-year-old patient also presenting mild intellectual disability, attention deficit/hyperactivity disorder, and truncal obesity. <b><i>Conclusion:</i></b> This paper confirms the role of <i>GNB1</i> in the pathogenesis of a classic rod-cone dystrophy and highlights the importance of including this gene in the genetic analysis panel for inherited retinal diseases.