The purpose of the study was to determine the effectiveness of 7E learning cycle model, which is based on constructivist theory and case-based learning (CBL), on students' achievement in and attitude to chemistry. A total of two hundred and eight (208) SSII chemistry students drawn from some selected secondary schools in three local government areas in Ibadan, Oyo state, Nigeria participated in the study. Two stimulus instruments were used: Teachers' Instructional Guide for 7E Learning Cycle Model and Teachers' Instructional Guide for Case-Based Learning Strategy. They were complemented with Chemistry Achievement Test (r = 0.81), Students' Attitude to Chemistry Questionnaire (r = 0.84), and Evaluation Sheet for Research Assistants. The study adopted pretest, posttest, control group, quasi-experimental design. Two hypotheses were tested at 0.05 level of significance and data collected were analyzed using analysis of covariance (ANCOVA). Multiple classification analysis (MCA) was used to present the magnitude of the mean scores while Scheffé multiple range test was used for post-hoc test to determine the source(s) of significant main effects. The results showed a significant main effect of treatment on students' achievement in chemistry (F [subscript (2,207)] = 4.584; p<0.05] and students in the case- based learning group obtained the highest chemistry achievement score (x-bar = 9.49) followed by those exposed to the 7E learning cycle model (x-bar = 8.40) while the conventional method group obtained the lowest (x-bar = 7.50); there was significant main effect of treatment on students' attitude to chemistry (F[subscript(2,207)] = 72.551; P<0.05] with the students exposed to case-based strategy obtaining higher attitude mean score (x-bar = 69.21) than those in 7E learning cycle model (x-bar = 68.87) and the conventional group (x-bar = 68.54).The two strategies, 7E learning cycle model and CBL, are more effective in improving senior secondary school students' achievement in and attitude to chemistry than conventional teaching strategy. However, CBL proved to be the most efficacious. Therefore, it is recommended that chemistry teachers should adopt constructivist/inquiry methods like 7E learning cycle model and case-based learning as these strategies will help students perform better in chemistry and also positively enhance the attitudes of many more students to the subject.