Background: A multitude of factors may influence fatigue in psoriasis and psoriatic arthritis (PsA); however, their individual fatigue components have not been thoroughly examined. Objectives: To explore characteristics of fatigue and its potential drivers in a cohort of patients with psoriasis with or without PsA. Methods: Adults with psoriasis and a nonpsoriasis control group completed the Multidimensional Fatigue Inventory-20 questionnaire. Patients with psoriasis also reported joint pain intensity, pruritus, skin pain, and sleep problems using a numerical rating scale. Linear regression models were applied to continuous outcomes, and beta coefficients (β) for the slopes were estimated with 95% confidence intervals (CIs). Results: Among 2741 adults with psoriasis (of which 593 also had PsA) and 3788 controls, the impact on total fatigue was greatest for PsA (β = 5.22; 95% CI, 3.55-6.90), followed by psoriasis (β = 2.10; 95% CI, 0.96-3.25), compared with the general population (P_trend <.0001). Among patients with psoriasis with or without PsA, increasing joint pain intensity was associated with overall fatigue (β = 2.23 [95% CI, 2.03-2.44] for each 1-point increase in joint pain numerical rating scale score). Limitations: We lacked information on the effect of pharmacotherapy. Conclusions: These findings highlight the importance of a symptom-based approach when treating psoriasis, rather than focusing on objective severity measures alone.