The Senegalese star was on the scoresheet for his new employers in the first match of the Saudi Pro League season, but saw his side fall to a 2-1 defeat to Al Ettifaq in what is Steven Gerrard's first win as manager of his new club.
Bursting into the penalty area, Mane, leading the line in Cristiano Ronaldo's absence, latched onto a cut-back from the byline to slot home from close range, with Henderson just a couple of feet away from him.
However, Al Ettifaq fought back in the second half and claimed the win through goals by Robin Quaison and former Celtic and Fulham striker Moussa Dembele.
Henderson played in his first league match for his new employers Al Ettifaq, whom he signed for at the end of July.
The Sunderland-born star was brought in by Liverpool legend Steven Gerrard who was named as the club's boss earlier in the summer, naming Henderson as the captain and handing him the no.10 shirt.
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While Henderson spent 12 years at Anfield, Mane enjoyed six seasons with the Reds as the midfielder's teammate, establishing himself as a fans' favourite.
In his time at the club, Mane scored 120 goals in 269 appearances for Liverpool, adding 48 assists as well.
With his Al Nassr career up and running, he'll be hoping to have a similar impact with his new Saudi employers.
It's not clear why Ronaldo was left out of the squad, however, he was substituted during their Arab Club Champions Cup triumph last weekend.