The study investigated the effect of audio-lingual strategy on secondary school students’achievement in Oral English in Ogun State, Nigeria. Oral English is a vital aspect of English Language learning that enhances learners’ listening and speaking skills. However, students’ achievement in Oral English has remained unsatisfactory, partly due to the continued use of conventional lecture-based instructional approaches. The study therefore examined whether the audio-lingual strategy would improve students’ achievement in Oral English. The study adopted a pretest-posttest non-randomized quasi-experimental design. The population comprised Junior Secondary School II students in public secondary schools in Ogun State. A total of 800 students participated in the study, with 400 students assigned to the experimental group and 400 to the control group. The Students’Oral English Achievement Test (SOEAT) with a reliability coefficient of 0.82 was used for data collection. Students in the experimental group were taught using the audio-lingual strategy, while those in the control group were taught using the lecture method. Data were analysed using descriptive statistics and Analysis of Covariance (ANCOVA) at the 0.05 level of significance. The findings revealed that students taught using the audio-lingual strategy obtained a higher mean achievement score (Mean = 10.14, SD = 3.07) than those taught using the lecture method (Mean = 7.45, SD = 2.78). ANCOVA results further showed a significant main effect of treatment on students’ achievement in Oral English (F(1,795) = 54.160, p < .05). The study concluded that the audio-lingual strategy was more effective than the lecture method in improving students’ Oral English achievement. It was therefore recommended that English Language teachers should integrate audio-lingual activities such as dialogue practice, imitation, repetition drills, and listening exercises into Oral English instruction.