Endon was born to Datuk Mahmood Ambak, a Malay man, and Datin Mariam Abdullah, a Japanese woman.

Endon met Abdullah while she was working at the Federal Establishment Office (now the Public Service Department) in the 1960s and they were married in 1965.

She left for St. John's Medical Center in Los Angeles, California for treatment, returning again in June 2005 for chemotherapy.

Endon Mahmoud was conferred the Tun Fatimah Award by the National Council of Women's Organisations on 24 August 2004 for her service to the community.

She was posthumously conferred the Seri Setia Mahkota Malaysia (SSM) which carries the title 'Tun' on 6 June 2009 in conjunction with the birthday of the Yang di-Pertuan Agong Tuanku Mizan Zainal Abidin.