Background: Even though health care seeking interventions have the potential to substantially reduce child mortality from easily preventable and treatable diseases, large number of children die without appropriate treatment and ever reaching the health facility and due to delays in seeking care in developing countries including Ethiopia. Objective: The objective of this study was to assess mothers/caretakers modern health care seeking behavior for common childhood illnesses and factors affecting it in Jeldu District. Methods: A community-based cross-sectional study was conducted in Jeldu District of West Shewa Zone, Oromia Regional State, from January 2011 to February 2011. A total of 433mothers/caretakers with under- five children who experienced diseases within six weeks before the survey were selected for this study. The study subjects were allocated to the selected kebeles proportionally to their estimated number of households and data were collected by using structured, pre-tested and interviewer administered questionnaire. The data entry and clearance were carried out using Epi Info version 3.5.1 statistical software package, whereas SPSS version 16 statistical software package was used for analysis. Results: A total of 422 mothers/caretakers were enrolled in the study giving an overall response rate of 97.5%. Of the total sick children reported, care was sought from health facilities for 315(74.6%). Care was sought first from health facilities for only 44%, while 30.6% sought health facilities after sought care from other sources. Marital status of the mothers (AOR=2.81; 95%CI: 1.54, 5.13), number of symptoms experienced by the child (AOR=1.98; 95%CI: 1.20, 3.36) and perceived severity of the illness (AOR=3.75; 95%CI: 2.24, 6.28) were identified as independent predictors of health care seeking practices from health facilities. Lack of money (40.2%) and perception that the illness was not serious (27.1%) were the main reasons given for failure to seek care from health facilities. Conclusion: Health care seeking practices of mothers/caretakers for common childhood illnesses were delayed (86.3%) and maternal/caretakers decisions to seek care from health facilities were widely influenced by worsening of the illnesses (61.0%). Thus, significant behavioral change effort should be taken to enhance the health care seeking behavior of the mothers/caretakers in the locality