In Garth Davis' feature, Patel plays Saroo Brierley, a young Indian boy who gets adopted by an Australian family, only to find his birth mother two decades later using Google Earth.
The actor said he fully committed himself to his role, according to The Hollywood Reporter.
"I called my manager straight after I walked out of the audition and told him that if I get it, don't send me anything for the next eight months. Don't distract me with any other work or audition.
The actor revealed that he auditioned for the role several times, including a Skype session from a bathroom. The actor said during a six-hour long audition process Davis asked him to roar like a lion.
"After the audition, (Davis) said 'If we decide to go with you. I really want you to change'. He said he wanted to see a Dev Patel that no one has ever seen before."
"Lion" also starring Nicole Kidman and Rooney Mara is scheduled to release on November 25.