The Tudors had been trailing 2-0 with 89 minutes on the clock as Sutton looked to be heading to the three points through goals from Tom Bolarinwa and Dan Fitchett.
But Michael Richens hit a sweet strike to give the Tudors a glimmer of hope, before Butler stepped up late on to launch a free-kick from deep inside the Hemel half straight into the top corner of the Sutton net to spark wild celebrations.
Today’s game was the fourth meeting of the sides this season, with the previous three having ended in two draws and a win for Sutton in the FA Cup.
Heavy rain left the Vauxhall Road playing surface looking heavy under foot, but this didn’t stop Sutton from making a quick-fire start as new Hemel signing Jack Kelly allowed Bolarinwa too much space on the edge of the box, and he beat his man before firing low and hard past Butler to open the scoring.
Hemel’s injury crisis has plagued them throughout the season, and the curse struck again after just 22 minutes as new signing Mat Mitchel-King was forced off with a hamstring problem, with Ollie Thorne coming on in his place.
Chances were at a premium in the first half hour, but Sutton striker Craig Dundas did well to turn on the edge of area before scuffing his shot tamely at Butler, while Ross Stearn saw a long range effort fly over the bar.
Hemel started the second half well and Sean Shields forced Sutton keeper Ross Worner into his first real save of the game as he let fly from 20 yards, before the same man beat the offside trap but was denied by a good covering block from Simon Downer.
Soon afterwards, ex-Liverpool striker Adam Morgan got onto the end of a decent cross from Graeme Montgomery, but he couldn’t quite direct his effort on target as it flew into the side netting from a tight angle.
Despite their slow start to the half, it was Sutton who struck next to double their lead in the 57th minute. A back-pass to Butler was caught up on the sodden turf before the ball was crossed low into the box where Fitchett was on hand to apply the finishing touch.
Hemel substitute James Potton looked lively after his introduction from the bench and he tested Worner with a decent effort, and the hosts came agonisingly close to reducing the arrears when Nikolay Todarov’s header came back off the inside of the post.
The Tudors kept plugging away, though, and they got their rewards late on when Richens fired home from the edge of the area, before Butler netted a few seconds from time to salvage an unlikely point.
Hemel Hempstead Town: 1 Jamie Butler, 2 Ben Herd (c), 3 Reiss Greeenidge, 4 Matthew Mitchel-King (15 Oliver Thorne, 22 mins), 5 Harry Hickford (16 James Potton, 63 mins), 6 Jack Kelly, 7 Sean Shields, 8 Michael Richens, 9 Adam Morgan (12 Jamie Slabber, 63 mins), 10 Nikolay Todarov, 11 Graeme Montgomery.
Subs not used: 14 Terrell Forbes, 17 Dennis Oli.
Sutton United: 1 Ross Worner, 2 Kevin Amankwaah, 3 Dan Wishart, 4 Dean Beckwith (c), 5 Craig Eastmond, 6 Simon Downer, 7 Tom Bolarinwa (14 Stuart Fleetwood, 84 mins) 8 Bedsente Gomis, 9 Craig Dundas, 10 Dan Fitchett (16 Tommy Wright, 86 mins), 11 Ross Stearn.
Subs not used: 12 Dan Spence, 15 Shaun Cooper, 17 Wayne Shaw.