Dia was born in December 9, 1981 in Hyderabad, Andhra Pradesh, India. Her dad's name was Frank Handrich, a German National, and an Interior Designer by profession, and her mom, Deepa, is Bengali-speaking. Deepa and Frank separated when Dia was 6, and Frank passed away three years later. Deepa then married Ahmed Mirza. The family lived in Khairatabad near Hyderabad and she completed her schooling in Vidyaranya High School and in Nasr School. Her step-father passed away during 2004.
She was introverted and unhappy as a child, and it was her parents, especially her mom, who instilled self-confidence and assisted her to break free from the barriers of low self-esteem.
At the age of 16, after completing her 10th standard, she got a job with Sriven Multi-Tech in Hyderabad. This job paved her way to modeling assignments with Lipton, Emami amongst others. With this exposure she was encouraged to participate in the 2000 Femina Miss India Beauty Pageant, which she did, came up the second runner-up and won three titles namely Femina Miss India-Pacific, Sony Viewer's Choice Award, and Miss Beautiful Smile. She went on to be crowned Miss Asia-Pacific on December 2, 2000 at Manila, making her the second Indian to win this award after a gap of 29 years.
Dia wanted to complete her graduation in Arts by correspondence, but decided to postpone it as it was becoming difficult to juggle between the Miss Asia Pacific Competition, modeling assignments, traveling and training. She was assisted by Sabira Merchant on diction and etiquette; diet with Anjali Mukherjee; gymnasium and physical fitness with Talwalkars; clothes from Ritu Kumar and Hemant Trivedi; skin care with Dr. Jamuna Pai; and make-up and hair-care from Bharat and Doris Godambe.
Dia made her debut on the tinsel screen with 'Rehnaa Hai Terre Dil Mein' during 2001, and thus was able to launch her career as an actress