Nonpharmaceutical interventions (NPIs), such as home isolation, social distancing, and infection control measures, are recommended by public health agencies as strategies to mitigate transmission during influenza pandemics. However, NPI implementation has rarely been studied in large populations. During an outbreak of 2009 Pandemic Influenza A (H1N1) virus infection at a large public university in April 2009, an online survey was conducted among students, faculty, and staff to assess knowledge of and adherence to university-recommended NPI. Although 3924 (65%) of 6049 student respondents and 1057 (74%) of 1401 faculty respondents reported increased use of self-protective NPI, such as hand washing, only 27 (6.4%) of 423 students and 5 (8.6%) of 58 faculty with acute respiratory infection (ARI) reported staying home while ill. Nearly one-half (46%) of student respondents, including 44.7% of those with ARI, attended social events. Results indicate a need for efforts to increase compliance with home isolation and social distancing measures.