Bangladesh is a country that has been intrinsically associated with natural hazards and disasters. ENSO is mainly a tropical event but its impact is global. El Nino represents the warm phase and La Nina represents the cold phase of the ENSO cycle.In this book, an effort was made to analyze the impact of ENSO on tropical cyclones and floods of Bangladesh using the data of depression and deep depression, cyclonic storm, severe cyclonic storm for the period of 1908-2007 (100 years) and rainfall for the period of 1948-2007 (60 years). These data were compared with the corresponding observations of SOI (Southern Oscillation Index).In case of depression and cyclonic storm there have significantly no variation for ENSO conditions but 54 severe cyclonic storms were formed during El Nino and 77 during La Nina condition in 100 years. Major 7 floods of Bangladesh having more than 35% affected area were identified. There was very excessive rainfall for the floods of 1955, 1974, 1987, 1988, 1998, 2004 and 2007. The analysis shows that 4 floods of 1955, 1974, 1988, and 1998 belong to La Nina condition, 2 floods of 1987 and 2004 belong to El Nino condition.