Chloe Lennon’s video, urging viewers to wear odd socks to celebrate the day on 21 March, has received over 13 million views on Facebook and has been shared more than 473,000 times across the world.
Chloe’s mother Jade, from Irvine, Ayrshire, said she filmed the clip to change perceptions of children with the condition and break down stereotypes.
Jade told BBC Scotland: “Chloe is just like any other five-year-old and it is heartbreaking when people take one look at her and assume she is not intelligent and she is not capable.
“She is capable, as are all people with Down’s syndrome.”
The video campaign has been a huge hit.
Jade said she had been contacted by people from around the world “inspired” by the video of her daughter.
She said: “I’ve had 7,000 comments and so many messages. I am so proud of Chloe for being such a positive influence.”
In the past, Jade said she had experienced “a few horrible comments” about Chloe’s condition, both online and in person.
Jade was contacted by well-wishers and lots of couples who had been told there was a chance their babies would be born with Down’s syndrome.
One American mother-to-be said she had been battling with a difficult decision about whether to continue with her pregnancy after doctors had diagnosed her baby with Down’s syndrome at 20 weeks. Jade said: “She didn’t know what to do. She told me she came across the video of Chloe, talked to her partner and showed it to him – and they have decided to go ahead with the pregnancy.”
World Down Syndrome day takes place on 21 March and aims to raise awareness of the condition while fundraising for charities.