The major purpose of this study was to find out the conceptions of science teachers about the nature of science. To guide this study, four research questions were asked and four hypotheses tested. The design of the study was descriptive survey and instrument used for data collection was a 22 item questionnaire. The sample of the study consisted of 400 science teachers drawn from senior secondary schools in Edo and Delta states. The data collected were analyzed with simple percentages and Chi square statistics. The major findings of the study included: (i) higher percentage of science teachers selected options which agreed with traditionalist's view on NOS; (ii) of the 22 items, in 17 of them a higher proportion of science teachers conceived science from the traditionalist's view as against 5 for the constructivist view; (iii) a significant difference between the proportions of science teachers who opted for either traditionalist's or constructivist's view in all items except item 11; (iv) non-significant difference between the proportion of male and female science teachers on conception of science from the traditionalist's view; (v) significant differences in the proportions of male and female science teachers only in items 6,8,9 and 12 on the conception of science from the constructivist's view; (vi) non-significant difference in the proportions of urban and rural science teachers on conception of science from the traditionalist's view while significant differences were found between them only in items 2,6,10,12 and 17 on constructivist's view; and (vii) non-significant difference in the proportion of NCE, B.Sc (Ed) and B.Sc holders on conceptions of science from the traditionalist's view in all items except in item 17 while significant differences were found between them only in items 4,9,17 and 20 on constructivist's view. It is concluded that this trend in the conception of NOS can only be reversed through a deliberate science teacher preparatory curricula reform to include elements of constructivism.