It's definitely not the first time the star has gone for a pants-style at a social event.
On March 16, Heinrich donned a black jumpsuit with silver zip detail for the Myer Fashion Runway show.
See also...
Anna Heinrich isn't afraid to take a risk with racing fashion.
The lawyer who rose to fame finding love with Tim Robards on Australia's first season of The Bachelor wore a cream Carla Zampatti pantsuit to the Star Doncaster Mile Inaugural Luncheon.
“I’ve always felt so good in a pair of pants,” Heinrich, 30, told Confidential.
“I don’t know if I’ll rock another suit at the races, but I’ll definitely be wearing it again soon in the future.”