The state dinner was the second to be co-hosted by Melania. It was held to honour Scott Morrison, Prime Minister of Australia, who attended with his wife.
Melania wore a turquoise J Mendel dress complete with vertical ruffles.
The outfit has been created by Gilles Mendel, a New York based designer.
Melania had previously wore one of his outfits during Trump’s first visit to Britain in July last year.
However her choice was criticised by Vanessa Friedman, the New York Times fashion critic, and others on Twitter.
In an article titled ‘Melania Trump’s Say Nothing Dinner Dress’ Ms Friedman said her outfit “wasn’t just understated, it was an absence of statement”.
Ms Friedman added: “But in a visual world, like it or not, we all demand more from our clothes.
“Is it really so strange that we’d expect the same from her?”
The dress Melania wore is no longer available in high end shops, but had been for sale for a reported $6,000 (£4,811).
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Mr Morrison because Prime Minister on 24 August 2018, replacing Malcolm Turnbull.
Mr Turnbull had been challenged for the leadership by right-wing home affairs minister Peter Dutton.
On Sunday the Australian leader pledged $150million (£120million) to support Trump’s planned mission to Mars.
He said the move would help the Australian Space Agency “foster the new ideas and hi-tech skilled jobs that will make Australian businesses a partner of choice to fit out Nasa missions”.
Mr Turnbull also visited Arlington National Cemetery in Washington DC, where he visited the tomb of The Unknown Soldier.
Earlier this week Melania attended the reopening of the Washington Monument.
The First Lady looked stunning as she attended the opening of the landmark after its three year renovation.
She could be seen wearing a structured white dress by Prada, which fell just below her knees.
The dress had a belt detail, which cinched in at Melania’s waist and accentuated her figure. She teamed the dress with a pair of printed heels, which added a pop of colour to the white ensemble.
She was joined by fourth grade students from Amidon-Bowen Elementary school, who she greets with high fives and handshakes.