BACKGROUND Blood transfusion is associated with potential risks of transfusion-transmitted infections (TTIs). Different strategies are needed to monitor blood safety and screen the donors' efficacy, such as evaluation of the prevalence and trends of TTIs. This study was conducted to evaluate the prevalence and trends of TTIs, including hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV), and human T-cell lymphotropic virus (HTLV 1/2), and the impact of the donors' characteristics such as age, sex, and donor status on the prevalence of TTIs in blood donors in seven large provinces of Iran from 2010 to 2018. METHODS This study was conducted on the data collected from all blood donations in seven Iranian Blood Transfusion Centers including Ardabil, Alborz, Guilan, West Azarbaijan, North, Razavi, and South Khorasan from April 2010 to March 2018. Demographic characteristics, number of donations, donor status, and screening and confirmatory serological results of all blood donations were collected from Iranian Blood Transfusion Organizations (IBTO) national database. The prevalence and trend of HBV, HCV, HIV, and HTLV 1/2 infections were reported according to the donation year and donor's characteristics. RESULTS The analysis of the prevalence and trend of TTIs in 3,622,860 blood donors showed a significant decreasing trend in first-time and regular donors. Additionally, compared to first- time donors, regular donors made safer blood donations with lower risks of HBV, HIV, HCV and HTLV 1/2 (P < 0.0001). Although the prevalence of HTLV 1/2 and HBV was higher in females, TTIs had a significant decreasing trend in males and females. Finally, it was found that the prevalence of HBV and HTLV 1/2 increased with age up to 40-49 years and then decreased thereafter. CONCLUSIONS The decreasing trends of TTIs in Iranian donors during 9 years may indicate that the various strategies implemented by IBTO have been effective in recent years. Other factors such as a decrease in the prevalence of specific TTIs in the general population might have also contributed to these declines.