The 17-year-old, whose chances have been limited since he became the club's youngest-ever player in 2008, stepped off the bench to fire his side to victory with a 60th-minute thunderbolt as the Lions ended their campaign with a whimper.
Millwall almost snatched a point at the death when Tamika Mkandawire saw his header come back off the upright, but it was the Tykes who held on to claim the win that secures their best finish since returning to the Championship five years ago.
Needing to inject some life into his toiling attack after a poor first half, Barnsley boss Mark Robins opted to introduce Noble-Lazarus for Jacob Mellis at the break - and within 15 minutes the youngster had made a stunning impact.
Jacob Butterfield had already forced David Forde into a good parried save with a long-range effort before youngster Noble-Lazarus took centre stage by collecting Nathan Doyle's pass and cutting inside before drilling left footed from outside the area with a superb shot that beat Forde all ends up.
Doyle came close to a second goal with 13 minutes left when he lashed the ball wide after working space well, before in the second of six minutes of injury time, Mkandawire was unlucky to see his header from James Henry's cross cannon back off the post.
Source: PA
Source: PA