The West Sussex airport handled more than 3.44 million passengers in June - a 3.3% rise on the same month in 2012.
The increase came despite North Atlantic traffic decreasing more than 12%. There were also dips in UK and Channel Islands traffic (down 2.4%) and in Ireland traffic (down 3.2%).
However, European scheduled service passenger numbers rose nearly 6% and long-haul traffic excluding North Atlantic rose more than 11%.
Gatwick's chief financial officer Nick Dunn said: "Gatwick achieved modest growth in June. This marked a return to the more restrained growth of earlier in the financial year, which is to be expected given the continuing strong economic headwinds. The small rise we saw this month was largely due to new airlines and routes which have started from Gatwick this year.
"Business destinations in particular continue to grow, with increased services to Scandinavia, Luxembourg and Copenhagen being introduced.
"EasyJet's new route to Moscow, which commenced earlier this year, continues to attract healthy passenger numbers thanks to the competitive rates on offer for both business and leisure travellers."