Gillies who was born in Tamworth started off working as a reporter, producer and news presenter for Prime Television in that region. During her ten-year association with Prime she became the face of Northern New South Wales. Her first role at Seven was an assistant producer on Seven's Late News with Anne Fulwood.
Prior to The Morning Show, Kylie's most recognised role at the Seven Network was on Sportsworld as the sports news presenter. She presented the sports news headlines at least twice during the program. Gillies is also a reporter for Seven's Australian Open Tennis coverage, providing the weather and the sports reports for each day of the Open.
Gillies was Weekend Sunrise sport presenter and regularly filled in on Sunrise if Natalie Barr, Mark Beretta or Melissa Doyle were away, taking their position reading the news, sport or presenting the show. She used to also regularly present Seven News late news updates, sharing the position with Chris Bath and Samantha Armytage.
In December 2006, Kylie was a regular presenter of the weekend sport report on Sydney's edition of Seven News, filling in for Nick McArdle, who has since left the network. Gillies has had experience presenting on Sunrise, Weekend Sunrise, Seven Morning News, Seven 4.30 News and Seven News in Sydney.
In June 2007, Gillies began her role as co-host on The Morning Show with Larry Emdur, which airs after Sunrise from 9:00 am to 11:30 am on weekdays.
In June 2009, Kylie announced that she would take part in Dancing With The Stars. She finished in third place.
In 2010, Gillies received a Walkley award for her contribution to journalism.
In April 2011, she presented reports for The Morning Show and Seven News live from London for the Royal Wedding of Prince William and Catherine Middleton.
Gillies has also been a fill in presenter on Today Tonight.
in 2014, Gillies and her The Morning Show co-host Larry Emdur, whose studio is just across from the Sydney Lindt Cafe, were able to view and report on the events of the 2014 Sydney hostage crisis, as the events unfolded, before transferring transmission to the network's Melbourne Studios
Gillies is married to journalist Tony Gillies and they have two sons Gus and Archie.