The event will be held in Pazardzhik, Bulgaria, at this end of this month.
GB Pentathlon have selected eight athletes for the championships – the four top ranked girls and boys in the country.
Denton, who swims for Plymouth Leander, is the youngest member of the squad at just 13 years-old. The rest of the team are all either 15 or 16. Denton, though, will turn 14 just days before the championships.
Both Denton and Mitchell will be making their debuts at the championships.
The rest of the girls’ team will be made up of Lancashire’s Emma Whitaker and Hertfordshire Kamie Lowe, while Yorkshire’s Toby Price and Joshua Hood, Somerset’s George Case and Kent’s Tom Wilton make up the boys’ team.
The individual events in Bulgaria will take place on June 30, with the relay events on July 2.