The deployment of innovative and learner-centered approaches into teaching and learning has strong potential of improving students’ learning outcomes. The study compared the effectiveness of computer simulation and animation instructional packages in flipped classroom settings on secondary school students’ achievement and retention in geography. The study adopted a pre-/post-test, non-equivalent, non-randomized quasi-experimental control group design. A sample of 126 senior secondary school class two (SS2) geography students was purposively drawn from two intact classes in Minna Metropolis, Niger State, Nigeria as participants for the study. The two intact classes were randomly assigned to experimental group I (computer simulation package, n=67) and experimental group II (computer animation package, n=59) in flipped classroom settings. A 50-item geography achievement test (GAT) was used for data collection, while computer simulation and computer animation instructional packages were administered to students as treatment in flipped classroom settings. The face and content validity of GAT was carried out using experts in the field of geography, educational technology and computer science from Federal University of Technology, Minna. GAT was further subjected to pilot testing, and a reliability coefficient of 0.85 was obtained using test re-test method and PPMC formula. Descriptive statistics of mean and standard deviation were used to answer the research questions, while inferential statistics of t-test was used to test the null hypotheses at 0.05 level of significance. Findings revealed that computer simulation (mean gain=41.70) and computer animation (mean gain=38.32) instructional packages in flipped classroom settings improved students’ achievement and retention of geography concepts. Also, no significant difference was found in the mean achievement (t=.05, df=124, p=0.63) and retention (t=2.04, df=124, p=0.82) scores of the two groups. It was therefore recommended that teachers should incorporate technology-based flipped classroom instructional strategies into teaching and learning of geography in order to improve students’ learning outcomes in the subject.