Evans was in imperious form after picking up the lead on the opening lap, and although his early momentum was rocked by the first-lap crash that caused a lengthy delay in proceedings, the Kiwi was able to break-build over polesitter Oliver Rowland throughout the race.
The win was cemented as Alexander Sims hit the wall in the stadium, eventually resulting in the introduction of the Porsche Taycan safety car that froze the order to allow Evans to collect his win - and the Jaguar driver heads into Sunday's finale 21 points behind championship leader Stoffel Vandoorne, who finished fifth.
Starting third, Evans got a good launch off the line to immediately battle for the lead, while Rowland's start was poor and was leapfrogged at the line by Lucas di Grassi and Evans.
This handed the Brazilian an early lead, di Grassi keeping the inside line for the first corner, but it ultimately lasted a mere seconds, as Evans spied an opportunity to send Jaguar down the inside of di Grassi at the next corner to collect the lead, in a bid to charge off into the distance.
But the race was then red-flagged after a multi-car pile-up at Turn 21, as Jaguar stand-in Norman Nato slipped into the barriers, and was followed in by Sebastien Buemi and Dan Ticktum.
Nyck de Vries joined them and submarined underneath Buemi's car; the Dutchman's halo kept him out of harm's way, as Oliver Askew, Andre Lotterer, Nick Cassidy and Oliver Turvey were also swallowed up in the incident.
After a half-hour clean-up operation extricated the cars and rebuilt the barrier, the race could resume. By this point, the circuit was beginning to dry up as the rain that had peppered the Sports Complex over the afternoon had abated.
Evans batted away Rowland - who had cleared di Grassi in the stadium before the race was stopped - at the restart with consummate ease, and began to forge a lead in his efforts to try and keep his hand in the championship.
By the halfway point of the race, Evans was two seconds to the good over Rowland, and the gap continued to steadily grow as the Kiwi had enough energy to invest into building his lead.
But Evans was then unsettled by a slight moment four laps from home as he locked up into Turn 22, admitting after the race that he was slightly distracted by the pitting Antonio Giovinazzi ahead of him - essentially halving a nearly three-second gap over Rowland to give the Mahindra driver a chance.
If Rowland had a glimmer of hope, it was immediately wiped out by teammate Sims who endured his third trip into the wall of the weekend, losing grip in the stadium complex and fatally wounding his Mahindra machinery.
It brought out an initial full course yellow period in the dying stages of the race, but that was followed up by a safety car to conclude the race and grant Evans his fourth win of the season.
Rowland was untroubled by di Grassi after the first lap, claiming Mahindra's first podium of the season to help the team leap above Nissan e.dams in the teams' championship.
Di Grassi thus collected third and became the first Formula E driver to break beyond the 1000 point marker, on the brink of his 100th race in the championship.
Jake Dennis collected the fastest lap of the race en route to fourth, as Vandoorne was fifth having had to manoeuvre his way past Jean-Eric Vergne to minimise any damage to his championship lead.
Vergne had earlier been in the wars with Edoardo Mortara, hitting his rear as the Venturi driver moved twice to keep the Frenchman at bay. This earned Mortara a penalty as Vergne was left with nowhere to go, but that proved a moot point as the Swiss ace retired later on with a puncture.
This put Mortara officially out of the championship running, and makes Venturi's life harder in the teams' championship as it lessened the hit that Mercedes took following de Vries' retirement.
Pascal Wehrlein was seventh ahead of Robin Frijns, who did well to avoid the pile-up and benefitted by moving up eight places from his starting berth.
Antonio Felix da Costa ended the race in ninth place, as Nick Cassidy employed a late attack mode strategy to move past Maximilian Gunther for the final point of the race.
Sergio Sette Camara fell back after impressing in qualifying, with Dragon Penske's energy saving once again lacking compared to the other teams, as Nato was last of the 13 classified runners.
Seoul E-Prix - Race results:
|1||9||Mitch Evans||Jaguar Racing|
|2||30||Oliver Rowland||Mahindra Racing||0.820|
|3||11||Lucas di Grassi||Venturi||1.393|
|4||27||Jake Dennis||Andretti Autosport||1.902|
|7||94||Pascal Wehrlein||Porsche Team||4.149|
|8||4||Robin Frijns||Virgin Racing||4.508|
|9||13||Antonio Felix da Costa||Techeetah||4.970|
|10||37||Nick Cassidy||Virgin Racing||5.325|
|12||7||Sergio Sette Camara||Dragon Racing||6.121|
|13||10||Norman Nato||Jaguar Racing||57.545|
|29||Alexander Sims||Mahindra Racing||4 Laps|
|99||Antonio Giovinazzi||Dragon Racing||6 Laps|
|48||Edoardo Mortara||Venturi||10 Laps|
|33||Dan Ticktum||NIO Formula E Team||30 Laps|
|23||Sébastien Buemi||DAMS||30 Laps|
|17||Nyck de Vries||Mercedes||30 Laps|
|3||Oliver Turvey||NIO Formula E Team||30 Laps|
|36||Andre Lotterer||Porsche Team||30 Laps|
|28||Oliver Askew||Andretti Autosport||30 Laps|
|View full results|