The agency says that in 2014 there were 97 cases of TB reported.
This compares with 74 cases being reported in 2013.
Dr Michael Devine, Public Health Consultant at the PHA, said the increase reinforced "the critical need for early diagnosis and specialist treatment".
"Increased awareness, particularly among groups at high risk, as well as health professionals, is central to this," he said.
"It is important that everyone is aware of the symptoms of TB, which include a prolonged cough, fevers and weight loss.
"If people are concerned about their symptoms they should contact their GP. Greater awareness can mean the condition is diagnosed and treated much earlier."
The figures were released ahead of World TB Day on Tuesday.
The number of tuberculosis (TB) cases in Northern Ireland has risen by 31%, according to the Public Health Agency (PHA).