An unforgettable night in the Welsh capital exploded into life after less than a minute as Rhys Patchell dived over after just 43 seconds for the game’s opening try.
The response from a powerful Montpellier side was emphatic as they ran in three quick-fire tries of their own inside the opening 20 minutes to build a substantial lead.
Recalled back rower Josh Navidi struck on the stroke of half-time to give the home side fresh hope – and in the second half the waves of home attack proved irresistible.
Montpellier threatened to implode at the start of the second half with Bismark Du Plessis and Robins Tchale Watchou both yellow carded in the space of 60 hectic seconds as Lloyd Williams stretched over to cut the lead to a point.
An intercept try from wing Alex Cuthbert then had the stadium rocking for the bonus point score before Navidi crossed again as brilliant Cardiff Blues rattled up 27 unanswered points.
A late Montpellier try saw them claim a try bonus point, but the final word went to Patchell who slotted a penalty with the last kick of the game to deny the French side a second point ahead of the return clash in France next Thursday night.
A late change to the line-ups for Cardiff Blues saw Dan Fish pull out in the warm-up with Jarrod Evans coming into the starting line-up at fly half and Patchell moving to full back.
And in a quite staggering start the home side were straight on the attack as Tom James raced up the left wing from the kick-off before play was switched and Patchell booted into space before picking up and dotting down after 43 seconds.
Cuthbert was then inches from collecting a telegraphed floated pass out wide for a free run in, but the wing just failed to take the ball from the night sky.
A breathless start to the game continued as the first real attack from the French side saw them fizz the ball through the hands to rattle up close before South African hooker Du Plessis broke tackles and front row partner Jamie Mackintosh flopped over the line.
It was end to end stuff as the next home attack saw Navidi and Rey Lee-Lo punch holes before Jarrod Evans almost exploited a defensive gap with his flicked pass back inside to prop Taufa’ao Filise.
Offside against Gavin Evans gave Paillaugue a simple kick to put Montpellier ahead and two minutes later a second visiting try followed as a high up and under, despite cries for obstruction on Patchell, released a stinging counter attack from Ben Lucas and Nagusa dotted down.
Montpellier were playing some dazzling rugby with ball in hand and more slick handling released the elusive Lucas into space and, with a penalty won, a hopeful high kick fell kindly for Julien Malzieu who raced to the corner for a 20-7 lead.
Centre Gavin Evans immediately charged down a clearing kick from Lucas but it ran dead as shell-shocked Cardiff Blues looked for a way back into the game after the sudden burst of away tries.
Wing James was proving the star for the hosts as he looked a real menace every time he attacked the Montpellier defence. And it was another attack sparked by him that gave Patchell a kickable penalty that just drifted right of the target.
Patchell looked to make amends moments later as he rolled out of two tackles, and when he kicked to the corner the pack drove Navidi over to cut the lead to 20-14 at the break.
A lively start to the second half saw Du Plessis finally break the patience of Irish referee Peter Fitzgibbon as he was yellow carded and from the resulting drive the pack splintered the visiting defence and Williams dived over from close range.
Another yellow card followed for Robins Tchale Watchou for an infringement in the act of scoring as Montpellier were suddenly reduced to 13 men.
Cardiff Blues failed to make the numerical advantage count, despite yet another lung busting run from deep from the impressive James, as the French side soon returned to a full complement.
Lucas missed a penalty for Montpellier, after a high tackle, before the key moment as Cuthbert raced out of the line to pick off a pass and raced 65 metres down the line for the bonus point.
Patchell added a penalty soon after to extend the lead before, with 13 minutes left, Navidi was at the end of an overlap to score brilliant initial work from scrum half Williams who darted down the middle.
Montpellier snatched a late fourth try after more forward play sent Charles Geli over, but the final word went to Patchell as his penalty sealed the win.
01m Patchell t Patchell c 7-0
07m Mackintosh t Paillaugue c 7-7
13m Paillaugue p 7-10
15m Nagusa t 7-15
20m Malzieu t 7-20
40m Navidi t Patchell c 14-20
44m Williams t 19-20
62m Cuthbert t 24-20
67m Patchell t 27-20
70m Navidi t Patchell c 34-20
77m Geli t Catrakilis c 34-27
80m Patchell p 37-27
Cardiff Blues: 15 Rhys Patchell, 14 Alex Cuthbert, 13 Rey Lee-Lo, 12 Gavin Evans, 11 Tom James, 10 Jarrod Evans, 9 Lloyd Williams; 1 Sam Hobbs (Jenkins 60), 2 Kristian Dacey (Lewis 60), 3 Taufa’ao Filise (Mitchell 48), 4 Jarrod Hoeata, 5 James Down, 6 Macauley Cook (Dolan 71), 7 Josh Navidi, 8 Josh Turnbull
Replacements: 16 Ethan Lewis, 17 Gethin Jenkins, 18 Craig Mitchell, 19 Scott Andrews, 20 Cam Dolan, 21 Tavis Knoyle, 22 Aled Summerhill, 23 Garyn Smith