Cash has already been allocated to ensure no one is turned away from hospitals during what may prove to be a difficult period, particularly with a flu epidemic predicted.
Mr Griffiths, addressing the NHS Confederation Conference in Cardiff, said: "The ability of the NHS to cope in this area is crucial and I am pleased to say that for the first time ever health authorities have given a guarantee about the treatment of patients over the winter months."
Mr Griffiths, who announced an extra pounds 9.5m funding last month, said he expected the money to be used by hospitals to improve emergency services and reduce delays in discharging patients.
Winter is a high demand time for all hospitals, but many parts of Wales have a greater than average because of the high rates of heart disease and chest complaints, and industrial diseases left by the mining industry. - Roger DobsonReuse content