Sheikh Khalifa bin Zayed, UAE President, Sheikh Mohammed bin Rashid, Vice President and Ruler of Dubai, and Sheikh Mohamed bin Zayed, Crown Prince of Abu Dhabi and Deputy Supreme Commander of the Armed Forces, conveyed their best wishes.
Sheikh Mohammed posted a video showing the Gate Building at Dubai International Financial Centre lit up with both countries' flags and pictures of the leaders.
"The Saudi National Day every year is an occasion dear to all of us. An occasion in which we renew brotherhood and establish love and proceed from it towards a better and more beautiful future of two peoples united by ambition that knows no bounds," Sheikh Mohammed wrote on Twitter.
"Congratulations to the Custodian of the Two Holy Mosques King Salman bin Abdulaziz, my brother the Crown Prince, and the Saudi people on their 91st National Day. Our two nations stand as one and we celebrate all your achievements. We look forward to a bright future together," Sheikh Mohamed wrote.
The kingdom’s national day falls on September 23 and marks the day when its founder, King Abdulaziz Al Saud, renamed the Kingdom of Nejd and Hejaz as the Kingdom of Saudi Arabia, in honour of his family name.
It was declared a national holiday by the late King Abdullah in 2005.
Dubai will mark the event with a light show on the Burj Khalifa. The tallest building in the world will light up with the colours of the Saudi flag between 8pm and 9pm.
There will also be a special Dubai Fountain show featuring the Saudi national anthem.
In Abu Dhabi, several Yas Island venues will also be bathed in green light, the colour of the kingdom's flag, and fireworks will mark the occasion at 9pm at Yas Bay.
Some of the attractions that will light up in green are: the Etihad Arena, Ferrari World Abu Dhabi, Yas Waterworld, Warner Bros World, Clymb, Yas Mall, Yas Plaza Hotels and W Abu Dhabi.