The union rejected a pay-increase offer of 2.5% on Wednesday
The Northern Ireland chairman of the Prison Officer's Association (POA) has confirmed that its members are being balloted on potential strike action.
The union rejected a pay-increase offer of 2.5% on Wednesday.
Finlay Spratt called the offer "a disgrace".
Prison officers are not legally permitted to strike and the Northern Ireland Prison Service (NIPS) has urged the POA to reconsider the pay offer.
Acting NIPS Director General Phil Wragg said: "The overall pay settlement of 2.5% is the best pay deal anywhere in the public sector.
"It represents over £1.2m in additional funding.
"The award is significantly higher than for others who are paid from the public purse and recognises the unique role prison officers play with the 23% increase in the Supplementary Risk Allowance.
"We believe this pay package is very good in the current economic climate and we would urge the respective staff association to reconsider it against a pay restraint of 1% for other public employees."
The package includes a 23% uplift of the Supplementary Risk Allowance from £2,000 to £2,460 and a consolidated increase for staff on lower pay scales.
It also represents a 1% non-consolidated, non-pensionable payment for staff on single points and band maximum and includes retrospective payments to staff backdated to April where appropriate.
