Ileana was born in Mumbai, Maharashtra as the second child to her parents Ronaldo and Samira. She has three siblings – older sister Farrah, younger brother Rhys and youngest sister Eileen. Her first name comes from Greek mythology. While growing up, she lived in Goa for about seven years.
During that time, the manager of the hotel her mother was working in, suggested that she should start modelling and fixed a meeting with Marc Robinson. Though initially reluctant, she was persuaded and her first portfolio was created in January 2003, which she described as a "disaster". She began gaining notice through photo shoots and ramp shows and her second portfolio was set up the following year, which landed her three advertisements from Electrolux, Emami Talc and Fair and Lovely. The latter, in particular, which was directed by Rakesh Roshan, gave her exposure and brought in several offers for acting in feature films