Dia was born to Frank Handrich, a German interior designer from Munich and Deepa a Bengali Indian.
She was born in Hyderabad, India. Her father, Frank Handrich, was a German interior designer from Munich and her mother, Deepa is a Bengali Indian. They separated when she was 6 years old.
Her father died when she was 9 and her mother remarried Ahmed Mirza who died in 2004. Dia retained her Muslim surname (Mirza) from her step father.
According to Dia, she suffered from "low self-esteem" as a child.
When living in Khairatabad, Hyderabad, she attended Vidyaranya High School for Boys and Girls, a school based on the teachings of Jiddu Krishnamurti and later Nasr School in Kushnuma.
She is proficient in Urdu, Bengali, Hindi, English. She currently resides on Veronica Road, Bandra (West), Mumbai. Dia Mirza was Miss Asia Pacific for the year 2000 and was also second runner up in the Femina Miss India 2000 beauty pageant.
She was assisted by Sabira Merchant on diction & etiquette; diet with Anjali Mukherjee; 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