People aged over 60 and the disabled had enjoyed free travel outside the national scheme – which runs between 9.30am and 11pm on weekdays, and all day at weekends and bank holidays – because of a council subsidy.
But the authority is withdrawing the concession at the end of the year, a move expected to save about 600,000 a year.
The UK's biggest pensioner organisation, the National Pensioners Convention (NPC),said the cuts were aimed at those "who could least afford it".
Dot Gibson, NPC general secretary said: "Hull City Council takes the prize for being the first local authority to show its meanness towards older people by cutting back on free travel.
"Thousands of local pensioners will need to use their passes before 9.30am in order to go to hospital and GP appointments – but now they will have to pay.
"Some councillors may consider this an easy way of saving money, but some older people will struggle to find the money for the fares. These cuts are clearly aimed at those who can least afford it."
However council leader Carl Minns said people would still be able to travel free after 9.30am – adding: "It's hardly a mean scheme.
"We are not the first to do it all. We were one of the few authorities that were going above the national scheme and it became increasingly unaffordable."
The changes will be introduced in January. People with concessionary bus passes will still be able to use them at any time over the weekend and throughout England.