Bronchiolitis is an acute lower respiratory tract infection in early childhood caused mainly by different viruses. Etiology of bronchiolitis have been studied in different environments and populations. Respiratory syncytial virus (RSV), human Metapneumovirus (hMPV), human Bocavirus (hBoV), human Rhinoviruses (hRV) have consistently been shown to predominate. Few studies however have attempted to determine whether other pathogens, particularly Mycoplasma Pneumoniae (MP) and Chlamydophila pneumoniae (CP), are associated with bronchiolitis in children under 2 years of age. The aim of this study was to determine the prevalence and clinical features of MP and CP in children under the age of 2 years presenting to the Iashvili Central Children Hospital in Tbilisi with various severities and clinical manifestations of bronchiolitis. Acute and convalescent serum samples were tested by ELISA for IgM and IgG antibodies to RSV, CP and MP.37 children under two years of age were studied. In 19 patients out of 37 (51.35%) etiological diagnosis were established and in 18 patients (48.65%) no pathogens were found. 11 patients (29.72%) had either CP or MP and 8 patients (21.62%) had RSV. Children infected with CP and MP had less severe bronchiolitis than those infected with RSV. Co-infection was not associated with disease severity. There were no statistically significant differences between groups with respect to length of hospital stay. Our study underlines the importance of atypical bacterial pathogens in acute bronchiolitis in children under 2 years and highlights the complex epidemiology and clinical features of these pathogens in this age group.