Background and Objectives: Tristeza is one of the most important viral diseases in citrus products worldwide. Fars province is one the most important citrus growing regions in Iran. Infection to citrus tristeza virus (CTV) has been reported from many citrus orchards in this region. The objectives of this research were to determine CTV distribution, evaluation of citrus species infection to CTV and to compare the infection prevalence rate to CTV in different regions of Fars province.Material and methods: This cross sectional study was performed on 230 samples collected from different citrus species grown in Kazeroun, Firouzabad, Ghir-o-Karzin, Jahrom, Darab and Fasa regions. First existence of infection to Tristeza virus was detected using ELISA. The prevalence of infection was calculated based on the rate of infection in the total numbers of samples. Next, a PCR amplification was performed based on the primers specific for coat protein and p23 genes.Results: Based on the ELISA test, all citrus species were infected to CTV. The virus infection was detected in all the regions of interest. Totally, 24.35% out of 230 collected samples were infected to CTV. The highest infection prevalence was found in Jahrom, Ghir-o-Karzin, D arab , Kazeroun, Firouzabad and Fasa, respectively. Furthermore, mandarin was found the most infected fruit between all citrus family, followed by lemon Lesbon, lime, orange and sweet lime, respectively.Conclusion: The results of this research showed that CTV infection has increased during the past years. As a result, control ofthe disease in this region is necessary.