Background: Psoriasis is a chronic inflammatory disease that can be influenced by nutritional status and dietary habits. In particular, adherence to the Mediterranean diet, known for its anti-inflammatory properties, is increasingly being investigated in relation to disease severity and nutritional status. Aims: This case–control study, including 50 psoriatic patients and 40 healthy controls, aimed to examine the correlation between adherence to the Mediterranean diet and disease severity, nutritional status, and disease presence in patients with psoriasis. Methods: The clinical severity of psoriasis was assessed using the Psoriasis Area and Severity Index (PASI) score. Anthropometric measurements were taken, and body composition was determined using bioelectrical impedance analysis. All participants’ Mediterranean Diet Adherence Screener (PREDIMED) scores and 24-h food consumption records were evaluated. Results: The body weight (BW), waist circumference (WC), hip circumference (HC), and fat mass (FM) values of psoriatic patients were found to be significantly higher than those of the healthy control group (p < 0.05). The PREDIMED score of psoriatic patients was found to be significantly lower than that of the control group (p < 0.001). A negative correlation was observed between the PREDIMED score and BW, FM, and HC (p < 0.05). PASI levels decreased as PREDIMED scores increased (r = −0.314, p = 0.048). According to logistic regression analysis, after adjusting for age and sex, the likelihood of being healthy was approximately 6.363 times higher in those with high adherence to the Mediterranean diet (p < 0.001). Conclusion: When psoriatic patients were compared with healthy controls, significant differences were observed in PREDIMED scores. Notably, greater adherence to the Mediterranean diet was associated with reduced disease severity, suggesting a potential mitigating effect even in the presence of obesity.