The 19-year-old Republic of Ireland Under-21 international captained United's Premier League 2 side for the first half of last season before moving to St Mirren in February, where he made 18 appearances as a deep-lying playmaker, scoring once and providing one assist for the Paisley club.
Devaney featured in Manchester United's pre-season fixtures against Wrexham and Rosenborg this summer, scoring in the latter, before United confirmed his fresh loan switch on Sunday.
Hibs head coach David Gray welcomed the move, praising the midfielder's profile.
"He's a technically talented young international footballer who is keen to learn and develop," Gray said. "To have him join before the end of the window is really positive and we'll look to get him settled in as quickly as possible."
Hibernian sporting director Malky Mackay said the club had fended off considerable competition to land Devaney.
"He's a young player with an excellent background and, importantly, he already has experience of playing in the Scottish Premiership.
"It's an exciting opportunity for Jacob and for the club, and we're really looking forward to seeing what he can bring to Hibs."
Devaney joined United's academy as a six-year-old and signed his first professional contract in 2023, going on to captain the club's under-21 side.
His previous loan spell at St Mirren gave him a taste of senior Scottish football, and Hibernian's option to make the move permanent suggests the Edinburgh club see the switch as more than a short-term arrangement.