Objectives: Ionizing radiation was known to cause disruption of cytoskeleton. However, the disorganization of the cytoskeleton leads to form microparticles (MP) that carry membrane and cytoplasmic constituents from their parent cells they are released from. Therefore, authors investigated the effect of the occupational exposure to low doses of ionizing radiation on MP levels. Material and Methods: The current study was conducted on 38 healthy medical workers occupationally exposed to low doses of ionizing radiation and 29 controls matched by gender, age, and smoking habits. The MP levels measured by flow cytometry were classified as positive or negative phosphatidylserine (PS⁺ or PS^–), and phenotyped according to their cellular origin. Results: Total MP (PS–/PS+) levels, regardless of phenotype, were significantly higher in workers occupationally exposed to ionizing radiation than in healthy individuals (p = 0.0004). Negative phosphatidylserine microparticles were predominant in medical exposed workers and, to a lesser extent, in controls (68% and 57%, respectively). With regard to phenotypic characterization of cellular origin, MP derived from platelets (CD41a+), endothelial (CD146+), leucocytes (CD45+) and erythrocytes (CD235a+) MP were significantly enhanced in exposed workers compared with controls (p < 0.0001). However, no significant difference was found in the proportion of the other blood elements in the peripheral circulation between the 2 groups. Serum levels of C-reactive protein were normal for all individuals. In addition, no association was observed between MP levels and the studied confounding factors. Conclusions: The results suggest that elevated circulating MP levels represent an indicator of cellular damage caused by medical exposure to low doses of ionizing radiation. By consequence, the quantification of MP seems to be a useful biomarker for assessing the negative effects of occupational exposure to ionizing radiation. Int J Occup Med Environ Health 2018;31(6):783–793