Medical staff checked 60 members of the Only Kids Aloud choir, from Wales, after they arrived at Heathrow Airport from Cape Town via Dubai.
The children's choir, with members aged between nine and 13 from across Wales, had performed at sell-out concerts in Cape Town.
They sang with Welsh opera star Bryn Terfel on Friday and Saturday night.
Bet Davies, of the Wales Millennium Centre, in Cardiff, which formed the choir, said the group was now on its way back to Wales.
She said: "Some were sick on take-off, some on landing and some during the turbulence.
"So, because of the rules in the airline industry - we were travelling with Emirates - they say if more than three children are sick on the same flight you need to have paramedics in to check on the children.
"We were also anxious that they were checked out before travelling back to Wales as we have a duty of care towards them."
She added: "The medics say it could have been somebody with a bit of a bug before they travelled, or it could be a combination of what I describe as nausea, tiredness and not drinking enough."
The children were later discharged.