"Beabea - wow! I'm so happy for you my dearest big sissy and dear Edo," she captioned the snaps.
"It's been a long time coming and you two are meant to be."
In an official statement, Princess Beatrice said: “We are extremely happy to be able to share the news of our recent engagement.
"We are both so excited to be embarking on this life adventure together and can’t wait to actually be married.
"We share so many similar interests and values and we know that this will stand us in great stead for the years ahead, full of love and happiness”
The couple will tie the knot in 2020 with more details to come in the following months.
Meanwhile, proud mum Sarah Ferguson has also taken to social media to congratulate her daughter and future son-in-law.
"I know what a mother feels so I have tears of joy. I am so proud of this sensational news. Andrew and I are just the luckiest people ever to have two great sons in law," she wrote on Instagram.
“Everything clicks when they are together and that’s exactly what my lens captured. It was an honour to observe and document such love.”