Princess Eugenie was praised for "respecting Saudi Arabian culture" as she flew to the country to support Princess Beatrice.
Princess Beatrice, 35, spoke at the Open Forum: Meet the 21st Century Entrepreneurs event in Riyadh over the weekend.
The event, part of the World Economic Forum, hosted several speakers including the Princess of York.
Princess Eugenie, 34, attended the event to hear her older sister speak in the discussion panel.
Princess Beatrice and Princess Eugenie were photographed in Saudi Arabia
X
Eugenie earned praise for wearing a long-sleeved black top underneath a sleeveless dress, in line with Saudi Arabia's modesty laws.
The princess wore her Erdem "Roisin" floral dress, which she first wore at Prince Philip's memorial service in 2022.
However, she paired the sleeveless outfit with a long-sleeved black top.
The website Tourist Saudi says: "To avoid offending local sensibilities, or be challenged by the powerful religious police, men and women should cover as much skin as possible."
Eugenie paired her long maxi dress with a long-sleeved black top
X
One fan wrote on Instagram: "Being Middle Eastern myself, I love the fact that she showed respect for the culture with the sleeves."
Another added: "Lovely, sophisticated dress with a pretty print."
One royal watcher commented: "I know she did it for modesty because of the location. But the dress is lovely and looks good on her."
Eugenie paired her dress with ballet pumps from Dune London which cost £85.
Princess Eugenie wore this sleeveless dress from Erdem
Erdem
LATEST ROYAL NEWS:
Princess Beatrice was one of the speakers at the event
X
Princess Beatrice spoke proudly on the panel about her involvement in the technological world.
She said: "The whole conversation around the social contract between business, entrepreneur and government is blending itself into this ecosystem.
"And you know, what I'm seeing as somebody that's been working with a lot of entrepreneurs is that they're really excited to take on this challenge."
The description for the event read: "With recent technological advancements, the ability to start and operate a business has become more accessible than ever. But what qualities distinguish successful entrepreneurs in the dynamic landscape of the 21st century?"