This study aims to investigate the long-term effects of the use of inductive and deductive teaching methodologies on the acquisition of English passive voice. To find answers to the questions, we prepared two teaching programs based on inductive and deductive approaches. Sixty-five pre-university students from were assigned as participants. These students were divided into two groups named as inductive and deductive. Both groups took two pre-tests. The first pre-test was administered in order to find out the homogeneity of both groups in terms of English proficiency level and the second pre-test was administered to find out how much background English passive voice knowledge they possessed. One of the groups was taught inductively and the other one was taught deductively. Three treatment sessions were conducted to present English passive voice. The study included three delayed post-tests which were administered four weeks, eight weeks and 12 weeks after treatment sessions. The analyses of the tests were conducted using descriptive statistics, independent samples test, and repeated-measures ANOVA. The analyses of the data revealed that both methodologies had significant effect on learning English passive voice. The inductively taught learners performed better in a short range of time. However, participants of the deductive group gained higher scores in a long range of time. Since the aim of the research was to investigate the long-term effects of the aforementioned methodologies, it was concluded that although inductive approach is efficient in the beginning, the deductive approach proves to be more efficient in the course of time.