Previous studies on family history of psoriasis showed that patients with a family history have an earlier onset of the disease, but such studies in Japan are still limited. To elucidate the characteristics of patients with familial psoriasis, we studied the family history of patients with psoriasis using the West Japan Psoriasis Registry, a multi-institutional registry operated by 26 facilities in the western part of Japan, including university hospitals, community hospitals, and clinics. This study enrolled 1847 patients registered between September 2019 and December 2021, with 199 (10.8%) having a family history of psoriasis. Patients with a family history of psoriasis had significantly earlier onset of the disease than those without a family history. Furthermore, patients with a family history of psoriasis had significantly longer disease duration. Psoriatic arthritis (PsA) was significantly more common in patients with a family history (69/199, 34.7%) than in those without a family history (439/1648, 26.6%) (adjusted P = 0.023). A subanalysis of patients with PsA revealed a significant difference in the patient global assessment (PaGA) score in Fisher's exact test and adjusted test. The numbers of patients with PaGA 0/1 were 29 (43.3%) and 172 (39.9%) in patients with PsA with and without family history of psoriasis, respectively, whereas the numbers of patients with PaGA 3/4 were 13 (19.4%) and 145 (33.6%) in patients with PsA with and without family history of psoriasis, respectively. Other disease severity variables did not show a difference between the two groups. Our findings suggest that genetics play a larger role in the development of PsA than in the development of psoriasis vulgaris. Most cases of PsA occur in patients who already have psoriasis, therefore dermatologists should pay attention to joint symptoms, especially in patients with psoriasis who have a family history of psoriasis.