The goal, just after the quarter hour mark, was enough for Hemel to claim the points after a disappointing performance by Chelmsford.
Charlie Henry saw his penalty saved by Jamie Butler midway through the first half – City’s second saved penalty in three days – as the Clarets toiled against a resolute Hemel side.
Chelmsford rallied late on but were unable to force Butler into any further action as Chelmsford suffered defeat in their first home game of the season.
Following Saturday’s 2-2 draw with Oxford, Clarets boss Mark Hawkes made just one change to his starting line bringing in Mark Haines following his suspension for Luke Daley.
Hemel Hempstead were looking to build upon an impressive start to the season after they beat Dartford at home at the weekend thanks to a solitary goal from Oliver Hawkins.
And it was the visitors who would take the lead just after the quarter hour mark through former Claret Jamie Slabber.
A whipped ball in from Ben Herd was headed back across goal by Oliver Hawkins, and after Rory McAuley slipped inside the area all Slabber had to do was poke home from six yards out.
Much like Saturday’s draw with Oxford, City failed to get started in the first half and almost fell behind further when Hawkins rose highest to a cross from the head but headed over.
But City were handed a way back into the contest when Billy Bricknell was adjudged to have been fouled by Michael Richens inside the area and the Clarets were awarded a penalty.
Having missed one on Saturday, Bricknell passed on penalty duties to Charlie Henry but he was also unable to convert from 12-yards as Jamie Butler guessed correctly, diving to his left to parry away to keep the visitors in front going into the interval.
Mark Hawkes – who was serving his second game of a two match touchline ban – retook his place in the stands for the second half as McAuley went close with his header from a Henry corner as City searched for an equaliser.
Hugo Skepelhorn struck the side netting after a lovely give and go gave the striker room for a strike, but some poor defending from Clarets almost allowed Terrell Forbes to double Hemel’s lead after the ball landed to the centre half but his fresh-air kick let City off.
Chelmsford’s best chance to level game with 20 minutes remaining when a corner was headed against the bar not one but twice by the same header by Harry Hickford, before a second header was punched over the bar by Butler.
City had a couple of other chances from set-pieces with sub Luke Daley heading over after a quick corner routine allowed Henry to lift the ball into the area. And Lee Sawyer’s header, from a flicked on Mark Haines throw in lacked the power to really trouble Butler as City failed to find a way past a stubborn Hemel back line.
The Clarets boss, who will return to the dug out for Saturday, will hope for a much improved performance from his side at the weekend as Chelmsford play host to Hayes & Yeading United.
1. Ashley Timms
2. Harry Hickford
3. Michael Toner
4. Mark Hughes (C)
5. Marvin Ekpiteta
6. Rory McAuley
7. Luke Daley
8. Lee Sawyer
9. Billy Bricknell
10. Charlie Henry
11. Hugo Skepelhorn
12. Harry Morgan
14. Jonah Gosling (On for Hugo Skepelhorn 74’)
15. Bagasan Graham (On for Charlie Henry 89')
16. Luke Daley (On for Harry Hickford 74’)
21. Connor Pearce
Hemel Hempstead Town
1. Jamie Butler
2. Ben Herd (C)
3. Kyle Connolly
4. Matty Harriott
5. Terrell Forbes
6. Matt Spring
7. Dennis Oli
8. Michael Richens
9. Oliver Hawkins
10. Jamie Slabber
11. Mo Shariff
12. Jamie Potton (On for Mo Shariff 45 + 1’)
14. Emmanuel Folarin
15. Jamal Lowe (On for Dennis Oli 38’)
16. Wilfried Ghanore (On for Jamie Slabber 81’)
22. Jamie Head
Chelmsford City: None
Hemel Hempstead Town: Jamie Slabber 16’
Chelmsford City: Rory McAuley (Foul – 33’), Mark Hughes (Foul – 74’)
Hemel Hempstead Town: Ben Herd (Foul – 28’), Kyle Connolly (Foul – 35’)
Referee: Daniel Cook (Portsmouth)
Assistants: Jonathan Creswick & Elliot Heward
City Man of the Match: Marvin Epkiteta