Background: Female reproductive tract infection including vaginitis is considered as one of the most public health issues and is known as a silent epidemic that might affect adolescents. Educational health programs are very effective in improving adolescent knowledge and practices regarding vaginitis and its preventive measures.

Aim: to assess the effectiveness of an online educational program on first year college girls’ knowledge about vaginitis and its preventive measures in Jordan.

Methods: a convenience sample of 120 participants of first year college girls' students were recruited and randomly assigned into intervention and control groups. A pre-test was conducted for both groups and a post-test was conducted 2 weeks after the intervention for both groups.

Findings: the results showed significantly higher mean and standard deviation in the intervention group (M= 26.17; SD= 3.24) compared to the control group (M= 17.49 (5.91) after conducting the educational program (p<0.00), this means that the educational program about vaginitis is effective in improving girls’ knowledge.

Conclusions and recommendations:  Using short 2-hour lecture, using an effective online and high-tech teaching methods and good follow-up would be very beneficial to improve the knowledge level among adolescents.