Background: H1N1 is a major cause for concern among the common people of India and needless to say it has created fear across various strata of the society. The novel viral infection which is caused by influenza type A virus is an acute respiratory infection and is also known as swine flu. Objective: The objectives of the study were to assess the knowledge regarding H1N1  among adults and to determine the association between level of knowledge regarding H1N1 among adults and socio-demographic variables.  Study design: Quantitative approach using descriptive design. Setting: Study was conducted at Ananthapuri Hospitals and Research Institute, Thiruvananthapuram. Population:Adults who are attending all out patient departments of Ananthapuri Hospitals and Research Institute, Thiruvananthapuram. One hundred and twenty adults attending outpatient departments were interviewed using structured interview schedule for assessing the knowledge regarding H1N1 among adults. Results: One hundred and twenty adults attending outpatient departments were interviewed. The collected data were analysed by using appropriate descriptive and inferential statistics The result revealed that only 18.3% of participants had good knowledge, 70.0% of participants had average knowledge and 11.7% of participants had poor knowledge regarding H1N1 among adults. Significant association was observed between the knowledge regarding H1N1 among adults with age (P value 0.002) and no association was noted with other variable like sex, religion, occupation and medias of information. Since the geographical areas of Kerala is now becoming more prone to the occurrence of communicable diseases, it is mandatory that all persons especially adults should be equipped with necessary knowledge regarding H1N1. So that they can act promptly if they encountered with such diseases. Conclusion: The study findings revealed that majority of adults had moderate knowledge regarding H1N1.