Operator, Fraport, notes that the "significant increase" was positively impacted by fewer public holidays last month than in May 2016, which was also affected by bad weather which caused a number of weather-related flight cancellations.
The latest figures mean than passenger traffic at Frankfurt Airport is up by 4.3% in the first five months of 2017.
Elsewhere across its global airport network, Fraport reports that passenger numbers increased at Ljubljana Airport (LJU) in Slovenia's capital city by a record 25.5% in May to 146,257 passengers.
Lima Airport (LIM) in Peru welcomed almost 1.7 million passengers (+4.4%) and the Twin Star airports of Varna (VAR) and Burgas (BOJ) on the Bulgarian Black Sea coast, combined, registered an increase of 3.8% to 238,128 passengers.
Its 14 Greek regional airports also performed well, says Fraport, registering a combined growth of 7.4% to 2.6 million passengers in May, while Antalya Airport in Turkey served some 2.6 million during the month, an impressive 38.3% more than the same period a year ago.
Hanover Airport in Germany (+9.5%), St Petersburg-Pulkovo in Russia (+26%) and Xi'an Xianyang in China (+14%) complete the happy picture.