New data has suggested that 40% of children aged between eight and 10 are talking to strangers online.
Figures released on Safer Internet Day by CyberSafeIreland show 79% of these children own a smart device capable of giving them access to the internet.
Almost one-third of them are speaking to strangers every day or at least once a week.
Many are also playing over-18s video games, containing violent or sexually inappropriate content.
CyberSafeIreland surveyed 1,200 children aged between eight and 10 in schools between September and December 2018.
The survey also found that 10% are online for more than four hours every day and that almost one-quarter of this group are playing over-18s games.
More than one-third of the eight to 10-year-olds are rarely or never talking to their parents about online safety.
CyberSafeIreland has said all children in this age-group who are online are potentially vulnerable - but those who are online without parental engagement are particularly vulnerable.
CyberSafeIreland CEO is Alex Cooney: "Our survey highlights that children are actively engaged in the online world from a young age.
"The vast majority of eight-year-olds have their own smart device, almost half are using social media, and one in five have appeared in a YouTube video.
"This is why we have launched a dedicated session for 3rd class this school year and it also why this Safer Internet Day, we have focused on developing a range of resources for parents of younger children, to help guide their decision-making around key issues like when to get that first device for their child".
CyberSafeIreland is highlighting the importance of parents engaging in their children's online lives, in order to protect them from risk but also to empower them to use the internet safely and responsibly.
They have also developed a flyer, with key advice around how to introduce the online world to children.
Copies of the flyer will be sent to 40 Early Start Centres around the country.
More information on CyberSafeIreland's Safer Internet Day campaign can be found here.