There were spurts of swine flu cases every year, even though the pandemic was over in August 2010. Most of the studies on swine flu pivoted around pandemic years 2009 to 2010. Here, through this retrospective study conducted at a tertiary care hospital in New Delhi, India, we compared clinical characteristics between H1N1-positive and H1N1-negative patients admitted in years 2015 to 2016. Among H1N1-positive patients, variables were compared among survival and death groups. Among 122 suspected H1N1 patients, 30 were positive for H1N1 reverse transcription–polymerase chain reaction. Symptom of rhinitis and low serum albumin were significantly more in H1N1-positive patients. Applying univariate analysis among H1N1-positive patients, respiratory rate, albumin level, alanine transaminase, aspartate transaminase, and Pao2/fraction of inspired oxygen (Fio2) ratio were statistically different between the survival and death groups. Further using simple logistic regression among H1N1-positive patients, Pao2/Fio2 less than or equal to 200 had an odds ratio of 9.2 (95% confidence interval [CI], 1.6–51.4), alanine transaminase level more than or equal to 40 U/L had an odds ratio of 7.3 (95% CI, 1.4–38.9), and albumin level less than or equal to 3.0 (gm/dl) had an odds ratio of 44.8 (95% CI, 4.0–497.4), and these were independently associated with death. After considering for causality/plausibility aspects, Pao2/Fio2 less than or equal to 200 had significant higher odds ratio of 12.3 (95% CI, 1.7–90.1) for death even if adjusted for age and sex. Hence, the value of Pao2/Fio2 at admission is a good predictor of mortality among H1N1-positive patients.