The Republic of Ireland Under-19 player made his Argyle debut last month in the 1-0 defeat by Sheffield United.
Plymouth boss Paul Mariner told the club website: "Joe's got a very bright future. He's been training with us for a number of weeks."
He added: "He's training very hard and whatever we throw at him he seems able to cope, and that's why he's with the first-team squad."
Source: BBC Sport
Source: BBC Sport