The figure accelerated from 5.7% in February, the Paris-based organization said in a statement, Anadolu Agency reported.
Headline inflation fell in 19 OECD countries, with the largest monthly decline seen in Slovakia.
Energy prices increased for the first time since last April, up 0.6% year-on-year.
Food inflation in the OECD eased further to 4.9%, from 5.3% the previous month.
Core inflation, excluding food and energy, however, was stable at 6.4%.
In the G20, annual inflation was constant at 6.9%, its highest level since March 2023.