The group, which includes Careshare and Nunu Nurseries, organised a year of fundraisers at all of its 71 settings to raise money for the Children's Acute Transfer Service at the hospital to help buy an ultrasound locating machine.
Through sponsored walks, dress-up days, cake sales and balloon races, the nurseries raised a total of £42,700, which was made up to £50,000 by the company.
The Doxford Park Nursery in Sunderland raised more than any other setting, with a total of £2,169. In recognition of their achievements, staff were invited to travel to London to present the cheque and go on a tour of the hospital.
Nursery manager Deborah Hogan said, 'It was a fantastic opportunity to present the cheque to Great Ormond Street. We were amazed to hear how much money had been raised.
'Fundraisers we held at the nursery included summer fayres, a sponsored walk to South Shields, book stalls and a balloon race. Our nursery cook even shaved her head. We wouldn't have raised so much money had it not been for our fantastic team of staff and parents.'
Jonathan Bell, managing director of Just Learning, said, 'Each individual nursery has done a fantastic job in raising such a large sum of money. Every member of staff has clearly put a lot of effort into arranging the fundraising activities. We surpassed our initial target by quite a substantial amount. I would like to thank everyone who donated for being extremely generous.'