Severe fever with thrombocytopenia syndrome (SFTS), caused by the SFTS virus (SFTSV), is a new acute infectious disease transmitted by ticks. Rickettsiosis is caused by Rickettsia spp. carried by ticks. Here, we conducted case analyses and molecular biological diagnosis of some patients with suspected SFTS in Liaoning Province in 2019 to identify rates of SFTSV and Rickettsia coinfection. Molecular diagnostic results confirmed SFTSV infection in 5 out of 17 suspected SFTS patients. Two strains of genotype A SFTSV were successfully isolated from patient blood. Ticks collected from the patient’s locations had high positivity rates for SFTSV, which was highly similar to SFTSV from patients. Antibody testing of 7 patient serum samples revealed all samples to be positive for Rickettsia antibodies. These results indicate coinfection of SFTSV with Rickettsia that may complicate disease presentation and diagnosis. Therefore, coinfection of tick-borne disease should be considered for correct diagnosis and treatment.