Pat O'Shane's clan is the Kunjandji people. Her mother moved the family from the small township of Mossman to dwellings near Cairns to enable her children to receive a good education. O'Shane ended up the only Indigenous Australian child in her age group graduating from her high school. O'Shane gained a scholarship and studied at Teachers' College and the University of Queensland, before teaching at Cairns High School for eight years. When her mother died she went into a deep depression and was hospitalised for four years. In that time she became dependant on prescription pills and was told she needed psychosurgery. O'Shane refused the operation and sought a second opinion, and was told the surgical procedure was unnecessary.
O'Shane immediately stopped taking her medication and threw out the pills she had become addicted to during her hospitalisation. While she weaned herself off the medication she worked and studied for a Bachelor of Laws degree at the University of New South Wales on an Aboriginal study grant. Three years later she graduated, and in 1976, she became the first Indigenous Australian to be admitted to the Bar. O'Shane found work with the Aboriginal Legal Services in Sydney and later in Alice Springs. After living in Alice Springs, she moved back to Sydney and tutored law at the University of New South Wales.
From 1981 to 1986, O'Shane was appointed as Head of the New South Wales Aboriginal Affairs Department; she was the first woman and Indigenous person to be the head of a government department in Australia. During this time, she was the Commissioner of the Commonwealth Tertiary Education Commission from 1983 to 1986. In 1986, O'Shane was the first appointed Indigenous Australian magistrate for the local courts in New South Wales. From 1995 to 2003, O'Shane was the Chancellor of the University of New England.