While Dortmund created the better of the chances at the Westfalenstadion, they failed to take advantage as Marc-Andre ter Stegen kept out Reus's spot kick shortly after the restart.
Barcelona manager Ernesto Valverde would have been pleased to see Lionel Messi come through half-an-hour unscathed after a calf injury, but the Spanish side will feel like they have gained a point after a below-par performance.
In-form teenager Ansu Fati got plenty of touches of the ball during the opening stages of the game, although both teams struggled to create clear-cut opportunities despite having joy in their respective final thirds.
The first notable chance went the way of Reus, who was denied by a fine stop by Ter Stegen after getting in behind the defence, before Mats Hummels sent a header marginally over the crossbar.
Achraf Hakimi also got in on the act as the right-back fizzed an effort just off target, but Barcelona soon began to build some momentum at the opposite end of the pitch, despite Jordi Alba needing to be substituted through injury.
However, for all of their possession and time on the ball in and around the Dortmund area, the Catalan giants were unable to force goalkeeper Roman Burki into any kind of save.
That soon changed after the restart as the stopper somehow managed to divert Luis Suarez's close-range effort past the post for a corner.
The opportunity was squandered, however, as Ter Stegen kept out Reus's shot from 12 yards, brilliantly diving to his left to get a hand to the ball before claiming it at the second time of asking.
The let-off prompted Valverde to introduce Messi into the action, but it was Dortmund who remained in the ascendancy as the game advanced into the final quarter.
Barcelona were being pushed further back into their own defensive third, and Ter Stegen needed to react sharply once again in order to keep out Reus's effort which was heading towards the bottom corner.
The visitors had more of the ball in threatening areas during the closing stages, although it would have been harsh on Dortmund had Messi's shot found its way through a pack of defenders in added-on time.
BORUSSIA DORTMUND (4-2-3-1):: Burki; Hakimi, Akanji, Hummels, Guerriero; Witsel, Delaney; Sancho, Reus, T.Hazard (Brandt 73'); Alcacer (Bruun Larsen 87')
BARCELONA (4-3-3): Ter Stegen; Semedo, Pique, Lenglet, Alba (Sergi Roberto 40'); De Jong, Busquets (Rakitic 60'), Arthur; Fati (Messi 59'), Suarez, Griezmann body check tags ::