There were two major purposes in this study and it was conducted in two stages according to these purposes. The purpose of the first stage was to examine prospective teachers' (geography, primary school and science) knowledge level about geography topics and to study department, gender and department x gender interaction effects on their knowledge level. The purpose of the second stage was to investigate the effectiveness of the teaching method based on the poster to learn the geography topics. The first stage used an ex post facto design. Sample of this stage consisted of 164 prospective teachers. Data of both the stages were collected with Geography Achievement Test (GAT, alpha = 0.81). Two-Way Independent-Samples ANOVA was applied to assess the effects of department, gender and the department x gender interaction. The results indicated that there was statistically significant difference between the departments' mean scores on GAT and department x gender interaction effects were not significant. The second stage used a one-group pretest-posttest design in order to investigate the effectiveness of the teaching method based on the poster to learn/teach the geography/science topics. Sample of this stage consisted of 47 prospective science teachers. The null hypothesis that there will be no statistically significant differences between the treatment group's mean scores of pretest and posttest on GAT was tested using One-Way Repeated-Measures ANOVA. In summarize, the prospective teachers' achievement level of the geography/science topics in the context of GAT was inadequate and the treatment was effective to learn/teach the geography topics. Teachers and curriculum development experts should favour the teaching method based on the poster for a successful geography/science education.