The deal followed the regrading of maternity support workers employed by Northern Lincolnshire and Goole NHS Foundation Trust earlier this year, Unison said.
Last summer, maternity support workers at Diana, Princess of Wales Hospital, Grimsby, carried out strike action over back pay.
The union said the outcome is another success of its Pay Fair for Patient Care campaign, which has won more than £200m for more than 40,000 healthcare workers since 2021.
Unison’s Grimsby, Goole and Scunthorpe health branch secretary Andrea Smith said: “Staff have been carrying out duties above their pay grade to make sure patients get the best possible care for years.
“It’s only right that they are regraded and fairly compensated for the work they’ve done previously.”
Ms Waters said: “It’s great news that so many staff will receive a pay rise in time for Christmas.”
The NHS Humber Health Partnership spokesperson said: “It is part of a national change, but we are pleased to have reached a collective agreement with our staff side colleagues.”