Ong was born and raised in Australia. In her late teens she began her modeling career. Ong married Australian electrical engineer Matthew Heath in 2009 after dating him for three years. They have a daughter Juliet born in 2010, and a son Harrison born in 2015. 
In 1999, Ong was signed by Jackie Chan to Media Asia in Hong Kong where she started a film career. She starred in her debut film Gen-X Cops. The success of Gen-X Cops was followed by a lead role in Rave Fever, an independent movie that established her as a serious actress.
She went to Hollywood where she had a small part in Pearl Harbor in 2001, but then shifted her acting career to Los Angeles where she was cast for several guest appearances in US TV series Las Vegas and Entourage.
Based in Singapore since 2004, Ong has co-starred with Thai actor Gof Akara and Sharon Au in Channel 5 drama Tiramisu. She is also a host for AXN, currently hosting and writing for eBuzz, a weekly entertainment magazine programme where she interviews international celebrities.
She also stars in Spa Seekers with her sister Lindsay on TLC.
She is a World Vision Singapore Goodwill Ambassador, travelling to Phuket, Thailand to learn more about poverty, HIV/AIDS and child prostitution issues. On her return, she participated in various World Vision events to help promote the charity. In December 2007, she was involved in a nationwide campaign for World AIDS Day called "One Life Experience".
- "Episode 1". Archived from the original on 19 August 2010.
- Kelvin Yang (1 Feb 2007). "One Life Experience (OLE): The Student Volunteer's Perspective".
- "Buy a M.A.C VIVA GLAM lipstick on December 6, 2008, and support a child living with HIV in Singapore through school!". World Vision Singapore. 1 Dec 2008. Archived from the original on 27 December 2009.
- "SAMSUNG OMNIA ON AXN'S EBUZZ".
- "Jaymee Ong's all revved up for the Singapore Grand Prix". 24 September 2008.