A quasi-experimental research design was used to investigate the change in science teaching efficacy scores after participation in the inquiry-based professional development program and the relationship of this change with selected independent variables. The data consisted of (a) three sets of Science Teaching Efficacy Belief Instrument (Riggs "&" Enochs, 1990) scores, STEBI-Form A (inservice), reported as a pretest, posttest, and follow-up posttest; and (b) demographic variables that were used as covariates: science education background, professional position, number of years taught, and teacher qualification status in science. Using repeated measures and multiple regressions with an alpha level of 0.05, and testing the hypothesized changes and relationships, results indicated that there were gains in Personal Science Teaching Efficacy (PSTE) and Science Teaching Outcome Expectancy (STOE) scores. Of the independent variables, only science education background was found to be a significant contributor toward increasing PSTE (p = .003) scores. The other variables were not predictive of gains in either personal science teaching efficacy or science teaching outcome expectancy