Deliveries by BMW's namesake brand rose 6.2 percent last month to 158,953 cars and sport-utility vehicles, the company said on Wednesday, citing strong demand in core European markets and China.
By comparison, Volkswagen's flagship Audi division sold 146,250 models, reporting an 11 percent gain on year-ago levels, while Daimler AG's Mercedes-Benz increased deliveries 13 percent to 150,742.
It was the second time this year that Mercedes-Benz, the third-largest luxury automaker by sales, beat Audi in monthly deliveries.
BMW is heading for a 10th straight year of leading the global luxury auto sales charts, but Germany's top three premium brands are closing ranks.
Munich-based BMW's overall 2014 sales lead over Audi has shrunk by a fifth to 43,000 cars after 11 months, compared with 54,000 at the same time a year ago.
Mercedes-Benz, which was eclipsed as top-selling luxury brand by BMW in 2005 and slipped into third place behind Audi in 2011, has narrowed its annual gap to BMW by 17 percent this year to 147,000 cars, compared with 177,000 a year ago.
"Premium demand looks set to remain strong as Mercedes has rejuvenated its fleet and Audi will start doing so next year," said Stefan Bratzel, head of the Center of Automotive Management think-tank near Cologne. "There will be no let-up in the luxury competition."