More than 230 people sought help with a gambling addiction last year.
It is a 7% increase on the 217 people who were assessed or treated for gambling as a problem in 2018.
The HSE says the figures come from the National Drug Treatment Reporting System but are not likely to capture all of those who were treated for gambling problems.
Brendan Kelly, professor of psychiatry in Trinity College Dublin, says the figures are the 'tip of the iceberg'.
"Addiction to gambling is far more common than is imagined," he said.
It's difficult to measure because there are people who are gambling in betting shops and people who are buying vast numbers of lottery tickets, but also there is online gambling, which is very concerning, and gambling by telephone in different age groups. The statistics only touch the tip on an iceberg.
Sinn Féin's health spokesperson, Louise O'Reilly, is calling for a gambling surveillance report to carried out.
"What the Department of Health needs to do is actually take an accurate picture because it's not just an issue around severe gambling addictions, it's actually around problem gambling," she said.
93% of those treated or assessed for gambling problems between 2015 and 2018 were male.