This study determined the efficacies of cognitive conflict and 5E instructional models on students' conceptual change achievement and self-efficacy in particulate nature of matter concepts in physics. In this study, non-equivalent groups quasi-experimental design was used. A sample of 195 senior secondary school year 1 students (SSI) with an average age of (M = 14.64, SD = 3.34) was used. Particulate Nature of Matter Conceptual Change Test (PNMCCT), and Particulate Nature of Matter Self-Efficacy Scale (PNMSES) were used to collect data. The SES was adapted and consists of 30 items of four-point Likert-type. A trial test was done on 20 SS1 physics students using the validated instrument. The estimate of internal consistency of 0.86 and a temporal stability of 0.99 were obtained for PNMCCT while an estimate of internal consistency of 0.71 was obtained for PNMSES. Before treatment, the initial conceptual change achievement and self-efficacy of the subjects were established using PNMCCT and PNMSES. After the treatment, the PNMCCT and PNMSES instruments were administered to the subjects as a posttest. Mean was used to answer the research questions while analysis of covariance was used to test the hypotheses at a 5% level of significance. The result showed that students' conceptual change achievement and self-efficacy were significantly enhanced after exposure to 5E instructional treatment than that of cognitive conflict. Thus, it was recommended that the 5E instructional model should be adopted by physics teachers for the effective improvement of physics students' self-efficacy in schools.