Azaylia Diamond Cain was diagnosed when she was just eight weeks old.
A fundraiser to try to help save her life had reached more than £1.5 million.
Posting an image of his daughter in his arms, Cain wrote on Instagram: “Rest In Paradise Princess.
“I will always hold you in my heart until I can hold you again in heaven.”
Azaylia’s mother Safiyya Vorajee also posted a picture of herself cradling her daughter.
She wrote on Instagram: “You are my angel, my heartbeat, my soul.
“RIP my precious baby, you will always be with me like a handprint on my heart.”
Cain had been raising money for Azaylia to get specialist cancer treatment in Singapore.
After a successful bone marrow transplant, her leukaemia had rapidly multiplied and she had gone into a full relapse.
Doctors told the couple that chemotherapy would not be enough to cure her.
In November, the couple made a plea for people to register as a stem cell donor after being told their daughter required a transplant, which led to 41,000 people applying within 48 hours.
Cain had previously told how his daughter “shows us all everyday how much she loves life and wants to be here”.
And Vorajee recently said she was feeling “heartache more and more” as “nurses woke me up this morning for a home visit and told me to enjoy the weekend as they now think her body is slowly shutting down…”
“I’m so proud of how strong you are Azaylia,” she wrote.
“Azaylia you’re my inspiration and my hero mummy loves you.”
Many took to social media to share their condolences on Sunday.
Love Island winner Jessica Hayes wrote: “I’m so sorry. I’m so sorry you have to go through such heartache. Holding you in my thoughts and sending you so much strength and love. Rest in peace beautiful Azaylia ð§¡ her strength and bravery had the biggest impact on us all .”
Mario Falcone said: “Heartbroken for you mate! Rip little Princess”.