The hosts started fantastically and almost took the lead just 80 seconds in when Nelson Weiper slashed wide of the near post, but their expectant fans did not have to wait long to see the deadlock broken.
Kaishu Sano - who had netted just once in his previous 76 appearances for the club - picked up possession near the halfway line, surged forward and rode several tackles before cutting inside and unleashing a curling 22-yard shot that took a deflection prior to finding the top corner, via the post.
It was all one-way traffic, and only a full-stretch fingertip save from Mike Penders, diving low to his left, prevented Stefan Posch from grabbing a second.
The Mainz No. 4 would not be denied with his next attempt, though, meeting the resulting corner with the sweetest of volleys that arrowed past the goalkeeper.
A rare chance for the visitors saw Guela Doue’s inventive flick land on the roof of the net, but they were all over the place at the other end, where Paul Nebel had a further effort superbly blocked.
The game’s pattern continued after the break as Phillip Tietz had a thumping drive beaten away at the near post by Penders, who thwarted the German again moments later by getting down low to palm an angled strike from inside the area to safety.
Strasbourg, who had lost on their three previous trips to Germany without scoring, then missed a golden opportunity to pull one back when Julio Enciso was picked out in space just 10 yards out, only to fire a tame shot at Daniel Batz.
That seemed to swing the momentum in the French outfit's favour, as Valentin Barco clattered a fierce strike against the post from close range before Diego Moreira’s similar attempt was kept out.
Nevertheless, Urs Fischer’s men subsequently responded, with three chances falling the way of Armindo Sieb. The first was superbly saved by Penders, but the forward may feel he could have done better with the other two, dragging one wide before failing to properly time his jump for a back-post header that ballooned up in the air and was cleared.
In the end, though, Mainz got the job done, winning a seventh successive home game in European football to put themselves within touching distance of the last four ahead of next week’s second leg.
Meanwhile, Gary O’Neil’s Strasbourg see their 10-match unbeaten run across all competitions come to an end, and they have an uphill task ahead of them in Alsace to turn this tie around and progress.
Flashscore Man of the Match: Kaishu Sano (Mainz)
