The poor performance of students in chemistry is often blamed on inadequate practical exposure during the teaching of chemistry due to hazardous nature of some chemistry experiments. Consequently, the search for teaching method that will be used to overcome this practical constraint has continued to engage researchers. Specifically, the main purpose of this study is to determine the effects of computer simulation on academic achievement of students in chemistry. Quasi-experimental research design, specifically, non-equivalent control group design was used. The sample consisted of 78 which is made up of 38 experimental group (18 males and 20 females) while control group was 40 students (16 males and 24 females) drawn from two coeducational secondary schools in Awka Education zone of Anambra State. Instrument used for data collection was Chemistry Achievement Test which was pilot tested for the period of one week in another zone. Scores obtained were used to estimate the instrument reliability which was found to be 0.78 Kuder Richardson formulas 20. Two research assistants were trained in carrying out the teaching using computer simulations. Pretest was given to the students before treatment. After four weeks of teaching, a posttest was given. Mean gain was used to answer the research question while hypotheses was tested with ANCOVA to determine the significance difference. The result revealed that computer simulation was more effective in enhancing students' achievement in chemistry than lecture method; there was no significant difference on students' achievement due to gender. It was recommended that computer simulation should be adopted for teaching hazardous chemistry concepts. Based on the findings, it was concluded that computer simulation should be employed in chemistry teaching as a means of improving students' achievement in the subject and providing a real life experiment for dangerous chemistry practicals.