Tanzania Journal of Health Research 2018; Vol. 20(4)Background: Chikungunya is an emerging mosquito-borne viral illness of major public health concern and is becoming a common infection in many geographical areas of Tanzania. This study was carried out to determine the incidence of malaria and chikungunya infections among febrile patients seeking medical care in Karagwe district, Tanzania. Methods: Febrile patients were enrolled into the study at Nyakahanga district designated hospital and Kayanga heath centre in May and June 2015. Questionnaires were administered to collect clinical and socio-demographic characteristics of patients. All participants were tested for malaria using malarial rapid diagnostic test and those tested positive by mRDT were confirmed by microscopy. Both outpatients tested malaria positive and negative were further screened for immunoglobulin M (IgM) and G (IgG) antibodies for chikungunya using enzyme-linked immunosorbent assay. Results: A total of 400 febrile patients were enrolled in the study. Out of 400 febrile outpatients tested for malaria, 116 (28.75%) tested positive with mRDT. Microscopy confirmed presence malaria parasites in 112 (96.55%) of the malaria RDT-positive. The overall seroprevalence of chikungunya infection was 24.25% (97/400). Out of those chikungunya seropositive subjects, 89 (91.75%) had no malaria. Co-infection rate of chikungunya and malaria was found to be 7.14% (8/112). Conclusions: Our findings confirmed the existence of chikungunya and malaria co-infection among febrile patients seeking health care in Karagwe district. Chikungunya should be considered in the differential diagnosis of malaria for appropriate case management and in order to monitor the public health burden and to inform possible preventative and control measures.