Behçet's disease (BD) is a disorder characterized by systemic inflammation of multiple organs, including the intestines. Several studies have reported a relationship between myelodysplastic syndrome and BD, and trisomy 8 was frequently seen, especially in intestinal BD. However, the association of BD with primary myelofibrosis (PMF) has not been well documented. A 58-year-old Japanese female was diagnosed with PMF in 2014. The symptoms of PMF resolved with ruxolitinib. However, she developed fever and intestinal perforation due to multiple ulcers in the terminal ileum in 2017. Intestinal perforation recurred 1 month later, and the dose of ruxolitinib was tapered. After discontinuation of ruxolitinib, she presented with recurrent oral aphthous ulcers and uveitis. Subsequently, intestinal perforation recurred, and she was diagnosed with intestinal BD. Trisomy 8 was identified in her peripheral blood. She underwent steroid therapy, azathioprine, and infliximab. This case suggests relationships between PMF, trisomy 8, and BD.