Ng was born in Indianapolis, Indiana, the first of five daughters, to Jin Ng and Virginia Fong. Her father, American-born of Chinese descent, was a financial analyst, and her mother, Thailand-born of Chinese descent, was a banker. She attended elementary school in Fresh Meadows, Queens and junior high on Long Island, New York. Her interest in baseball started when she played stickball on the street in Queens and her father taught her about sports. She played tennis and softball at Ridgewood High School in Ridgewood, New Jersey and graduated in 1986. She graduated from the University of Chicago in 1990, where she played softball for four years and was named MVP infielder, and earned a A.B. in public policy.
Ng began her career as an intern with the Chicago White Sox after graduating from the University of Chicago. She was hired full-time in 1991 and became special projects analyst before being promoted to Assistant Director of Baseball Operations under then-GM Ron Schueler in 1995. In 1995 she became the youngest person, and the first woman, to present a salary arbitration case in the major leagues when she worked for the White Sox, regarding the case of pitcher Alex Fernandez, and won. She then worked in the offices of the American League in 1997, where she was Director of Waivers and Records, approving all transactions.
In 1998, she was recruited by General Manager Brian Cashman to work for the New York Yankees as Assistant General Manager, becoming the youngest in the major leagues, at age 29, and one of three women (the other two are Elaine Weddington-Steward of the Boston Red Sox and Jean Afterman of the New York Yankees) ever to hold the position. She joined the Los Angeles Dodgers as Vice President and Assistant General Manager in 2001.
In 2005, Ng was interviewed for the vacant position of Dodgers general manager. No female has ever been a GM in any major sport. The Dodgers hired Ned Colletti as their GM, who immediately kept Ng on as his assistant. She has interviewed for the general manager position with the Seattle Mariners, San Diego Padres and Anaheim Angels. On March 8, 2011, Ng announced that she was leaving the Dodgers to take on the position of Senior Vice President of Baseball Operations for Major League Baseball, where she would report to former Dodgers manager Joe Torre.
Ng ranked #13 on Forbes Most Influential Minorities in Sports List in 2015
Ng ranked #5 on Forbes Most Powerful Women in Sports in 2015
Ng was named one of Adweek's Most Powerful Women in Sports in 2017
Ng and her husband Tony Markward, co-owner of Silas Wines in Oregon, reside in downtown Lower Manhattan in New York City.