S. pneumoniae is a component of normal nasopharyngeal flora in children. Nasopharyngeal colonization in children attending daycare units has an important effect on the spread of S. pneumoniae. In this study, we aimed to investigate colonization status, antimicrobial susceptibility, and clonal relatedness of the S. pneumoniae strains in children attending a daycare unit. One hundred and six nasopharyngeal swabs were collected from 25 children attending a daycare unit in an 8-month period. S. pneumoniae was identified by a conventional method. Antibacterial sensitivities of the strains were tested by disc diffusion method. Pulsed field gel electrophoresis (PFGE) was used to analyze the clonal relationship of the strains. A total of 25 (23.5 %) S. pneumoniae strains were identified from 106 nasopharyngeal swaps. S. pneumoniae growth was detected in at least one culture of the 19 children (colonization rate; 76%). Seven of the 25 strains (28%) showed resistance to penicillin, 5 (20%) were resistant to trimethoprim-sulfomethoxsazole. The other tested antibiotics were almost effective. The clonal relationship among strains was found as 54.5%. The highest rate of strain entry was in the winter months with strains of opaque colonies, which are known to be more pathogenic. However, the spreading rate among the children was the highest in the summer months and the strains detected in these months had transparent colonies with more transmitting characteristics. Therefore, to prevent S. pneumoniae infection in closed crowded areas, the summer months should not be overlooked.