The study evaluated the awareness of professional service of Quantity Surveyors among Private house owners in Nigeria (Osun State. Appraisal of relevant literature remained the basis for measuring awareness of professional service of Quantity Surveyors which has formed the frame work for designing Questionnaire used for the primary data .Two hundred numbers of Questionnaire were administered, One hundred and eighty were received. The questionnaire was analyzed using descriptive statistic, percentage and relative important index. The results of the analysis show that the reasons for not engaging the service of Quantity surveyors I do not understand the roles of Quantity surveyor was ranked first 0.67, followed by To avoid extra cost of their professional service 0.66 and third Lack of legislation that compels their engagement 0.65.The study concluded with recommendation, Individual client should be more enlightened about the importance and function of a Quantity Surveyor by organizing public lectures, workshop and seminars. Nigeria Institute of Quantity surveyors should liaise with government to engage professional service in formulating building act through legislation that will mandate clients to hire the services of Quantity Surveyors.