Vaccination against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the most desired solution to combat COVID-19. Understanding the willingness to accept vaccines is essential to make appropriate strategies for the vaccination programme's success. There was a lack of published literature in India among medical students. Hence, we conducted this online, cross-sectional study to assess the knowledge and willingness to accept COVID-19 vaccines among undergraduate medical students of a medical school in Delhi. A complete enumeration of all the undergraduate medical students was done. All the students were invited to participate in this online survey. The questionnaire through Google forms was shared through email and WhatsApp. The questionnaire contained questions on the socio-demographic details, questions related to the knowledge and perceptions about COVID-19 vaccines, willingness to accept the vaccine and vaccination status of the participant. Descriptive and multiple logistic regression analyses were carried out. Out of 320 students contacted, 298 consented to participate in the survey, and 274 participants (85%) completed the questionnaire. Three-fourths of the participants were male; the mean age of the study participants was 19.6 years. Only 70.4% were willing to accept the vaccine. Those who perceived COVID-19 vaccines as safe (AOR= 3.946; 95% CI: 1.946 to 7.912); and effective (AOR= 2.079; 95% CI: 1.054 to 4.101); and who has knowledge about the vaccines (AOR= 2.206; 95% CI: 1.186 to 4.104) were more likely to accept the vaccine. There is a need for enhancing the knowledge on vaccines, and their safety and effectiveness to promote the vaccine acceptance.