Background: Emergency Contraception (EC) is used after unprotected sexual intercourse, following sexual abuse, misuse of regular contraception or non-use of contraception. Seventeen percent of pregnancies in Kenya are unintended, potentially leading to unsafe abortion that contributes to the high maternal mortality rate in Country. According to 2016 Kenya Demographic and Health Survey (KDHS), the maternal mortality ratio was 362 maternal deaths per 100,000 live births. Female students in University or College are vulnerable to unplanned pregnancies and illegal abortions resulting in mortality, morbidity and psychosocial problems. Knowledge on EC is very important for students as they are not in stable relationships and not using regular contraception. Therefore, the aim of this study was to determine the knowledge and use of Emergency Contraception among female undergraduate students in the University of Nairobi. Materials and Methods: We used an institution-based cross sectional, quantitative study among 383 female undergraduate students at the University of Nairobi. The University of Nairobi has six colleges and systematic random sampling was used to select study participants from each college. Data were collected using self-administered questionnaires and analysed using SPSS Version 16. Bivariate analysis and logistic regression were used to determine sample characteristics significantly associated with knowledge and utilisation of Emergency Contraception. Results: Most (53%) Contraception knowledge on bivariate analysis were: age 20 years and above (p = 0.001), enrolment in college of health science (p = 0.001), being in year three of study and above (p = 0.0001) and having an insurance cover (p = 0.021). Ever use of Emergency Contraception was associated with enrolment in the College of health science (p = 0.025) and age 20 years and above (p = 0.050). In multivariate analysis, older age (Aor 1.885 p = 0.003) as well as being in the College of health science (Aor < 0.001) were significantly associated with increased probability of being knowledgeable about Emergency Contraception. Conclusion: Although University of Nairobi female undergraduate students are aware of the existence of Emergency Contraception, their specific knowledge on correct timing of taking EC after unprotected sex and on effectiveness is poor. EC use is also low, compounded by underutilisation of public facilities as a source of the EC and underutilisation of health workers as a source of EC information. Therefore, an educative forum may be needed to improve the knowledge of EC among University of Nairobi female students. Health education on the availability of EC in public facilities needs to be addressed. Possible use of informal sources of information such as peer education could be an area to explore in client education on EC knowledge and use. Further research is recommended to establish factors that influence utilisation of public health workers as a source of EC information.