Around 700 people took part in the 3km run, where they had paint thrown over them while they were competing.
The runners included Mike and Fiona Illingworth, from Witney, whose disabled 12-year-old son Ollie sounded the horn to start off the race.
Ollie regularly visits the hospice after he and his twin brother Ben – who died in 2012 – were born with the life-shortening condition MPS.
“I just want to say that my family, friends and myself thoroughly enjoyed taking part in the Oxford Rainbow Run,” said Mike.
“We had a crazy time, getting showered in a kaleidoscope of different colours, smiles and laughter all the way around.
“The money raised will make a huge difference to the lives of families like ours living in Oxfordshire and families from surrounding areas.”
The hospice is hoping to have raised £50,000 from the run, with another event due to take place in Reading next month.
Poppy Hanbury, activities fundraiser from Helen & Douglas House, said: “It was a fantastic day and everyone had great fun getting covered in paint all the colours of the rainbow.
“There were lots of smiles and laughter with everyone having a lot of fun.”
