"To my wonderful sister on her birthday," she wrote alongside the photo. "You are a wonderful mother and beautiful friend x I love u x Victoria."
To my wonderful sister on her birthday. You are a wonderful mother and beautiful friend x I love u xVictoria pic.twitter.com/qhQQT8FZ3V— Victoria Beckham (@victoriabeckham) November 22, 2014
Victoria, 40, who also has a brother called Christian, is the eldest of the Adams children.
Louise, who is married to communications manager Darren Flood, is mum to four children – Liberty, Tallulah, Finlay and Quincy.
So much fun with my family last night! I love u Louise and Christian x Victoria pic.twitter.com/gxTNLbZgRU— Victoria Beckham (@victoriabeckham) April 28, 2014
The former Spice Girl is very close to her sister and the pair are often spotted dining together in London. Louise also joined her parents Jackie and Tony Adams, as well as Victoria's husband David Beckham, at the opening of her flagship store on Dover Street in September.