Pillage’s selection follows last weekend’s British Open Modern Pentathlon Championships were he finished fifth overall and third junior.
He will be joined in the GB team in Barcelona by Bradley Sutton, Jamie Harper, Holly Parker, Zoe Davison and Charlie Follett.
It will be the second year running Pillage has competed at the Junior European Championships.
He will go to Spain in decent form. He won the British Modern Tetrathlon title earlier this year and finished sixth and Britain’s top male athlete at the Milan Kadlec Memorial.
The men’s qualifying at the Junior European Championships will be on Monday, with the final on Wednesday. The relay events will take place between Thursday and Saturday.
Meanwhile, Plymouth College pentathletes Annabel Denton and Georgia Mitchell have both reached the final of the Under-19 European Championships.
Denton, 14, topped qualifying Pool A in Poland, with Mitchell crossing the line in seventh. The final will take place on Friday.