The grandstands and verges were packed to capacity around Circuito de Madrid Jarama, and fans - as well as King Felipe VI, who was also in attendance - were treated to an instant classic of a race with da Costa leading Evans, Wehrlein and CUPRA KIRO's Ticktum across the line with less than a second between them.
Da Costa had started third and was first to jump into the pits for his stop on Lap 12. He pushed through the laps to take ATTACK MODE late on - matching up those around him out-front as the PIT BOOST stops shook out.
That teed up a real sprint to the finish with da Costas mirrors full of the fast-charging CUPRA KIRO of Ticktum on home soil for the Spanish car brand. The Brit made a stunning move stick around the outside of Wehrlein as the top four jostled on Lap 21 for second, with Evans following for P3 at the final chicane.
Evans then spotted his chance to go and sliced by Ticktum to take the fight for victory to teammate da Costa. The Kiwi thought the win was his, but he couldn't quite make a move stick with da Costa placing his Jaguar in all the right places to hold on to the flag to seal back-to-back victories with his new team.
Wehrlein pipped Ticktum to third as the KIRO driver made a last-ditch move on the Jaguars - Ticktum and CUPRA KIRO would still be mighty pleased with fourth.
Edoardo Mortara (Mahindra) rounded fifth with the outfit looking strong on pace - teammate Nyck de Vries compromised his own front-running race through a shunt with Wehrlein that was later penalised.
Sebastien Buemi (Envision Racing) wound up sixth after a late charge. Jake Dennis (Andretti) and Nico Mueller (Porsche) came home seventh and eighth with Pepe Marti - an early race leader much to the joy of the Spanish crowd - bagging points with ninth. Joel Eriksson (Envision Racing) completed the top 10.
All that sees Pascal Wehrlein top the Drivers' table - 11 points clear of Mortara. Da Costa jumps to fourth.
Jaguar close in on Porsche in the Teams' and Manufacturers': now only four points in the former and three in the latter.
We head to Berlin for Rounds 7 & 8 of the ABB FIA Formula E World Championship on 2 & 3 May.
As it happened...
Cassidy fired away to lead the field through Turn 1 with de Vries and da Costa eventually filing in-behind up the hill. Ticktum launched from ninth to fifth - hassling the factory Porsche in his CUPRA KIRO.
Lap 3 and at the hairpin, de Vries clipped the rear of Wehrlein's Porsche - launching his Mahindra into the air and dismantling his front wing in the process. He did manage to emerge in fifth, losing just a couple of spots to Guenther and teammate Mortara.
Ticktum had found his way into second just behind Cassidy, before slipping behind Wehrlein at the end of Lap 3 through the final chicane. The Brit was looking the part, though, early on, and managed to make it back by Wehrlein a lap later; the two trading spots by the tour.
Lap 5 saw Felipe Drugovich (Andretti) the first driver to take his mandatory 50kW, all-wheel drive ATTACK MODE boost; six minutes to use. By the end of his boost, the Brazilian had carved his way up to the race lead by the end of that boost on Lap 8 on the way up Turn 9 - some effort from the Mahindra driver.
That shunt early on was deemed de Vries' fault; a five-second penalty for the Mahindra driver for that contact with Wehrlein.
Drugovich led Cassidy, Wehrlein, Ticktum, da Costa, Mortara, Marti - in ATTACK - Guenther, Dennis and Nato rounded out the top 10 on Lap 9. A lap later and Marti made use of the rest of his ATTACK to hit the front to the joy of the home support - heading Cassidy and Ticktum.
PIT BOOST windows opened on Lap 11, and at the end of the lap a gaggle of cars led by da Costa jumped into the pit lane.
Lap 13, and di Grassi took P1 as his ATTACK MODE drew to a close. The PIT BOOST leader looked to be da Costa. We would see once the rest of the field took on their 30 second jolt of energy where things would ultimately shake out.
And on Lap 15, it did work out as anticipated. Da Costa took the lead on Lap 16 as the remaining drivers pitted. However, a well-timed ATTACK MODE deployment saw Guenther take P1 with 10 seconds of his 50kW all-wheel drive boost remaining.
The top 10 as it stood all elected to jump for their ATTACK MODE boost late on. Da Costa matching up Buemi who'd charged to P2 on Lap 19, with Mueller, Wehrlein, Cassidy, Ticktum, Mortara, Evans, Nato and Guenther rounding out the top 10.
With three laps left it looked da Costa's to lose with energy in-hand, an ATTACK MODE overlap and prime position out-front.
It was a furious sprint to the finish with five cars in one frame. Ticktum made a stunning move stick around the outside of Wehrlein on Lap 21 for P2, with Evans following for P3 at the final chicane.
Evans swooped around the outside of the CUPRA KIRO on the hairpin's banking to make it a provisional Jaguar one-two.
The Kiwi tried the same move a lap later for the lead on his teammate but da Costa held fast to take a breathless race win.
Follow the race LIVE on web and in the Formula E app!
Keep across Live Timing – which includes a real-time interactive track map and the ability to follow your favourite driver during every session of every E-Prix – plus highlights, detailed session reports, exclusive interviews, all the standings and results as well as data, insight and reaction from trackside.
LIVE: Follow every lap live, with reaction and coverage at fiaformulae.com/live
Additionally, Formula E’s social media channels, website, and app will provide session reports, exclusive interviews, and behind-the-scenes insights from trackside during the five-day event.
Find out more
WATCH: How to watch every Formula E race in your country
UNMISSABLE: Watch the brand-new season of 'Driver' on Amazon Prime
CALENDAR: Here's every race set for the 2025/26 Formula E season
FOLLOW: Download the Formula E App on iOS or Android
TICKETS: Secure your grandstand seats and buy Formula E race tickets
HIGHLIGHTS: Catch up with every race from Formula E IN FULL
HOSPITALITY: Experience Formula E and world-class motorsport as a VIP