Voice and text chat systems in the popular Fortnite game are leaving children open to being contacted by strangers, warns the NSPCC.
The warning comes after research by the charity suggested 25% of children had been contacted online by strangers.
It advised parents to turn off the voice chat system in the game to ensure children avoided inappropriate contact.
But the charity warned that the text messaging system in the game could not be disabled.
Options in the main settings menu in Fortnite did not let players block text messages sent to them, said the NSPCC.
It also advised parents to closely monitor the amount of money their children were spending through the game's online store, which lets keen players buy skins and other items to personalise their in-game avatar.
Fortnite is believed to have about 45 million registered players, with up to three million playing it at the same time.
One analytics site suggests that, on YouTube, it has surpassed Minecraft in terms of the popularity of videos showing people playing it.
The findings on contact from strangers emerged during regular research connected with the NSPCC's Net Aware app.
This gathers information for parents on how to oversee the way their children use top apps and games.
"Apps, sites, and games such as Fortnite: Battle Royale can be great opportunities for young people to play and engage online," said Laura Randall, the NSPCC's associate head of child safety online.
"In light of emerging concerns about the risks children could be exposed to, we are urging parents to be aware of Fortnite's features," she said.
A spokesman for Epic declined to comment on the NSPCC's claims.
Ms Randall said it was "vital" that parents talked to their children about the games they played and how they could avoid harm.
The NSPCC said parents should:
- let children know they could talk to them if upset or worried by anything they had seen online
- familiarise themselves with what their children did online and understand why they liked particular apps or games
- agree family rules on how to use apps, sites and games
- use privacy settings and parental controls to keep children safe