Meghan, who returned to the Games a year after her public debut with Harry, wore a black Emilia Wickstead Dress.
After the Saturday morning event at the Royal Botanic Gardens, Harry was joined by Markle at The Domain park for a reception at The Pavilion restaurant with Prime Minister Scott Morrison and leaders from support groups for veterans.
In the statement confirming Meghan's pregnancy, her mother Doria Ragland was mentioned, but Thomas' name was kept out of the message after he was said to have embarrassed his daughter and 34-year-old Harry after being paid to stage paparazzi photographs before their wedding.
The Invictus Games, Harry's brainchild and the focus of this tour, were founded by the prince in 2014.
Meghan, Duchess of Sussex, talks to students while riding on a tram in Melbourne, Australia, Thursday, Oct. 18, 2018.
"It's been an exhausting week, and although the Duchess hasn't had any morning sickness, she has been very exhausted", Royal reporter Emily Andrews said on Twitter this morning. "She said she was up at 4:30 a.m. this morning doing yoga in her room as she couldn't sleep".
Prince Harry and Meghan are due to fly to Queensland's Fraser Island on Monday before heading to Tonga and Fiji.
Emily said: "Meghan told me that she's feeling pretty good so far, which is great, and that she's running on adrenaline". This week, the newly-married couple was in Australia, and they flaunted more PDA than EVER! "Harry had to walk straight past Jenna to get to his and Meghan's table", a witness told Vanity Fair's royal correspondent Katie Nicholl.