Dries Mertens curled in from 18 yards in the first half to become Napoli’s joint top scorer of all-time, level with Marek Hamsik on 121 goals.
But Barcelona equalised after 57 minutes when Antoine Griezmann scored from Nelson Semedo’s low cross.
The visitors ended the sport with 10 men as Arturo Vidal was once despatched off late on.
In the 89th minute, he fouled Fabian Ruiz, but then, after the Napoli man reacted, Vidal pushed his head into the midfielder’s face and was shown two yellow cards in speedy succession
The return match takes vicinity at the Nou Camp on Wednesday, 18 March, though the Spanish La Liga leaders will also be without suspended midfielder Sergio Busquets as he picked up his third booking of this season’s tournament.
It came early in the second halfwhohen, with a foot raised, he caught Mertens, who limped off and had to be changed quickly afterwards.
Barcelona had an injury worry of their own as centre-half Gerard Pique hobbled off in introduced time at the end of the match with an ankle injury.
Napoli had probabilities to go into the second leg in Spain with the lead but visiting goalkeeper Marc-Andre ter Stegen made two first-rate saves, denying Lorenzo Insigne and then Jose Callejon.