Background: Teenage pregnancies is a global health problem affecting about 16million women each year, accounting for about 11% of all births. It affects mostly low and middle income countries especially in sub-Saharan Africa and southern Asia, and approximately 95% of all teenage pregnancies occur in these countries. The risk factors for teenage pregnancies are low socioeconomic status, early marriages, religious factors, low education levels and inadequate reproductive health and family planning services. Teenage pregnancies result into consequences such as maternal complications like fistula, post-partum hemorrhages, preeclampsia, unsafe abortions, low birth weight and increased infant mortality rate. Furthermore, it increases the rates of school dropouts and family dependents. Some interventions have been done like provision of youth-friendly and non-judgmental sexual and reproductive health services countrywide, however the challenge remains that teenagers still don’t get due to misconceptions and lack of awareness of the right to access them. Objective: To determine the knowledge, attitude and perceived causes of teenage pregnancies among secondary school students in Moshi Municipality, Kilimanjaro region. Methodology: This is a descriptive cross-sectional study which was carried out in July, 2016 in three secondary schools namely, Karanga, Kiusa and Korongoni Secondary schools in Moshi Municipality. 237 girl-students (age 13-18years) from form I-IV were enrolled through simple random sampling. Data was collected through structured self-administered questionnaires. The information collected were knowledge and attitude about teenage pregnancies. Data was entered in Microsoft access data base for cleaning and were analyzed using SPSS Version 20. The analysis was done and presented in frequencies and percentages using charts and tables. Results: Among 237 participants, 22.8% were form I, 21.1% form II, 28.3% form III, and 27.8% form IV. The mean age was 16years (SD=1.25). Christians were 75.9%, 23.6% Muslims and 0.4% Hindu. Inhabitants Chagga and Pare were abundant among the ethnic groups 54% and 14.8% respectively. 45.1% were aware of the correct meaning of teenage pregnancy, 68.8% had a basic knowledge on fertility and conception. Lack of health education and access to sexual and reproductive health information as well as peer influence were the leading causes of teenage pregnancies 71.7% and 68.8% respectively. Also have a negative attitude towards it due to its xi negative effects such as dropping out of school and unemployment 73.4% agreed, being a burden to family and the society 71.7% agreed and social discrimination as agreed by 49.8%. Conclusion: About half of students have the basic knowledge on teenage pregnancies, fertility and conception and are aware of the factors contributing to them. Also they have a negative attitude towards it. The Ministry of Education, teachers, parents and facilitators should work hand in hand to ensure this problem is alleviated. Researchers should do more studies on teenage pregnancies so as to cater for the information gap.