Background: Streptococcus pneumoniae infection in children usually begins with nasopharyngeal colonization that may be a significant risk factor for invasive pneumococcal disease. In this study it is aimed to determine the nasopharyngeal pneumococcal carriage rate in preschool- aged children, penicillin resistance rates of the isolated strains, risk factors for S. pneumoniae carriage. Materials and methods: Two hundred and fourteen children attending preschool were included in our study. The demographic characteristics and possible risk factors for pneumococcal carriage were investigated. Chi-square test and logistic regression model were used for statistical analysis. Results: Nasopharyngeal samples were taken from 214 healthy preschool children. No statistical difference was found between carrier and non-carriers with respect to age, gender, having respiratory tract infection within the last three months, presence of smokers in the family and number of people in the family. Thirty four of 214 children were unvaccinated against pneumococcus and 6 patients (17.6%) of these 34 children were found as S. pneumonia carrier. While 50% of pneumococcal isolates were susceptible to penicillin, the rate of high-level resistance to penicillin was 16.7% and intermediate level resistance rate was 33.3%. The pneumococcal carriage was found significantly increased in unvaccinated children compared to vaccinated children (P<0.0001). Conclusion: In our study the nasopharyngeal pneumococcal carriage rate was 2.8% in children aged between 4 and 6 years. This rate is lower than the data previously reported. Carriage was not seen in vaccinated children in our study. We think that routine pneumococcal vaccination is the major factor underlying this decrease. These results should be supported with multicenter studies.