The monarch greeted the High Commissioner of India and the Ambassador of Armenia, who spoke to her via video-link from Buckingham Palace on Tuesday.
Wearing a vibrant orange dress, the 95-year-old head of state chatted to the diplomats as they presented their credentials.
Gaitri Issar Kumar, the High Commissioner of India, in traditional Indian dress, gave a namaste greeting, while Armenian ambassador Varuzhan Nersesyan, in a morning suit, bowed to the monarch.
On Monday, the Queen held her first in-person engagement since catching Covid, meeting Canadian Prime Minister Justin Trudeau.
Mr Trudeau said at a Downing Street press conference afterwards that the monarch was “as insightful and perspicacious as ever”.
He later tweeted: “It’s always wonderful to see Queen Elizabeth II.
“When we met at Windsor Castle, we spoke about a wide range of issues – including global affairs, the situation in Ukraine, and Her Majesty’s lifetime of service to Canada and the Commonwealth.”
A photograph taken during the audience at Windsor featured a large bouquet of blue and yellow flowers, the colours of the Ukrainian flag, behind the Queen and Mr Trudeau.
The gesture was seen as a symbol of the Queen’s support for the people of Ukraine.
