The monarch, 95, held virtual audiences at Windsor Castle via video-link on Tuesday afternoon.
It is the first time she has been pictured undertaking her royal duties since Philip, 99, died peacefully at the Berkshire royal residence on April 9.
She held audiences with the Ambassador from the Republic of Latvia and the Ambassador from the Republic of Cote d’Ivoire.
The Queen had resumed royal duties just four days after the death of the Duke of Edinburgh.
The monarch hosted a ceremony to mark the retirement of her household’s most senior official, former Lord Chamberlain Earl Peel, on April 13.
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The Duke of Cambridge pledged to uphold Philip’s wishes and continue to support his grandmother the Queen and “get on with the job”.
Following Prince Philip’s death, it was announced the monarchy and their households would observe two weeks of royal mourning - with members of the family “continuing to undertake engagements appropriate to the circumstances,” a royal official said.