The veteran Xavi Hernandez was introduced at half-time with the Catalans trailing 1-0 to the Ligue 1 club at the Allianz Riviera stadium.
And he equalised from the penalty spot midway through the second half after Romain Genevois was adjudged to have fouled young forward Munir El Haddadi.
Earlier, Argentinian striker Dario Cvitanich had put Nice in front from the spot after he himself had been brought down by Gerard Pique.
New Barcelona coach Luis Enrique handed starts to summer signings Marc-Andre ter Stegen and Jeremy Mathieu, while Ivan Rakitic and Alen Halilovic were among a raft of players brought on as substitutes.
Barça's next friendly will be against Napoli on Wednesday. Their opening game in La Liga will be against Elche on 24 August.