Foreign tourists accounted for 140,456 of the total, while domestic tourists numbered 19,383, the statistics office said in a statement on Thursday.
Tourist overnights rose 3.3% on the year to 499,322 in May, with foreigners generating 437,268 of the total.
Visitors from France accounted for 13.1% of tourist overnights spent in Montenegro in May, followed by tourists from Germany with 12.6%, the United Kingdom with 11.2%, and Serbia with a 10% share.
Seaside resorts attracted 89% of all overnight stays, followed by the capital Podgorica with 6.1%, mountain resorts with 2.4% and other resorts with 2.1%.