Lack of basic knowledge about reproductive health, pose a serious health threat to adolescents. This study examined the effects of health education on knowledge of reproductive health among public secondary school students in Rivers East Senatorial District, Rivers State, Nigeria. The quasi-experimental research design was adopted with a population which consisted of 94,499 students. The sample size of 540 was selected using the multistage sampling procedure. Data was collected using a test instrument titled ‘‘Asking young people about sexual and reproductive health behaviours: Illustrative Core Instrument’. Data was collected in three phases – pre-intervention, intervention and post-intervention phase. All analysis was done with the aid of Statistical Product for Service Solution (SPSS V-27). Data were analyzed using descriptive statistics such as mean and inferential statistics such as ANCOVA at 0.05 alpha level. The result showed that health promotion had significant effect on the knowledge of contraception effect [F(1, 252) = 4.87, p<0.05], knowledge of antenatal [F(1, 252) = 7.175, p<0.05], and knowledge of postnatal care [F(1, 252) = 1.08, p<0.05]. It was concluded that health education is a very effective intervention that has the potential to influence knowledge of reproductive healthcare among secondary school students. It was recommended among others that the government should complement the efforts of NGOs by mapping out collaborative effort with continuous campaign for contraception among secondary school students to sustain the effect of the health education intervention.