Abstract: Psoriasis (PsO) is a chronic inflammatory skin disorder presenting in multiple subtypes, including plaque, guttate, inverse, pustular, and erythrodermic forms. A subset of patients eventually develop psoriatic arthritis (PsA), a distinct inflammatory condition characterized by concurrent cutaneous lesions and musculoskeletal involvement. The clinical spectrum of PsA encompasses peripheral arthritis, enthesitis, axial spondylitis, dactylitis, and nail involvement, with patients at elevated risk for systemic inflammation and comorbidities such as cardiovascular disease, inflammatory bowel disease, uveitis, and metabolic syndrome. Emerging epidemiological evidence reveals a bidirectional relationship between obesity and psoriatic disease. The global rise in obesity prevalence parallels increasing incidence rates of both PsO and PsA, with adiposity recognized as an independent risk factor for disease onset and progression. Obesity is associated with higher disease activity, impaired quality of life, and reduced therapeutic responsiveness in PsA patients. Furthermore, obesity differentially affects treatment efficacy across therapeutic classes, particularly diminishing the response to TNF-α inhibitors while IL-17 and IL-12/23 inhibitors retain relatively consistent effectiveness regardless of BMI. This review systematically examines current evidence focusing on two dimensions: the pathogenic influence of obesity on the development and progression of psoriasis and psoriatic arthritis, and its weight-dependent modulation of pharmacological interventions. By elucidating obesity' s multifaceted impact on disease pathogenesis, clinical manifestations, and therapeutic outcomes, this review aims to guide precision management strategies to improve disease control and long-term prognosis in affected populations.