This study examined the effectiveness of Inquiry Training Model on achievement in science of secondary school students. A purposive sample, consisting of eighty four eighth standard students of a government secondary school in Kozhikode district of Kerala State was adopted and a pre-test -post-test quasi-experimental design with a 2 x 2 factorial matrix was applied for the study. A regular class consisting of forty two students was taken as the control group and they were taught through conventional teaching approach during the experiment. Another division of eighth standard was taken as the experimental group and they were administered Inquiry Training Model by the investigator. The experimental intervention was carried out for a period of five months. Three hypotheses••were tested. Results of the ANCOVA analysis revealed that teaching science through Inquiry Training Model was more effective as compared to the conventional teaching. The analysis also revealed that gender has no effect on achievement in science and that there was no group gender interaction effect due to the intervention through Inquiry Training Model.