The rapid increase in the integration of technology in teaching and learning has changed classroom interaction, where a learner-centered approach has replaced the teacher-centered approach, leading to improved student participation in the teaching and learning process. The study was conducted to examine the effect of video-based assisted instruction on students' academic performance and knowledge retention in the concept of biological digestion at OLL Senior High School in the Kassena Nankana Municipality of the Upper East Region. A pre-test, post-test non-equivalent control design was adopted for the study. A convenience sampling technique was adopted in sampling two intact classes for the study. One class was assigned as control group and was taught through traditional method, and another class was assigned as experimental group and was taught through video-based assisted instruction. The instruments used for data collection were pre-test, post-test, retention test, and a questionnaire. The data was analyzed using descriptive statistics (percentage, mean, and standard deviation) and inferential statistics (t-test). The results of the pre-test proved that there was statistically no significant difference in the mean scores of students in the control and experimental groups, (t(48) = 0.59, P = 0.73). The results of the post-test also revealed that there was statistically significant difference between the post-test mean scores of students taught digestion through video-based assisted instruction and those taught through traditional method, (t(48) = 2.31, p =0.00). The study also proved that there was statistically significant difference in knowledge retention between students taught digestion through video-based assisted instruction and those taught through traditional method (t(48) = 3.09, p =0.00). The study also found that students had positive perceptions towards the adoption of video-based assisted instruction in teaching and learning the concept of digestion (weighted mean =4.26, SD= 0.63). It was concluded that video-based assisted instruction is an effective teaching method capable of improving students’ academic performance and knowledge retention in the concept of digestion. It was therefore recommended that video-based assisted instruction should be adopted by biology and integrated science teachers in teaching the concept of biological digestion.