It attributes the all-time high to the Easter getaway, which contributed to the airport handling a record of 6.5 million passengers (+5.5%) in March.
The airport has now experienced 17 consecutive months if traffic growth.
According to the airport, long-haul, emerging destinations were some of the best performers, as Heathrow reported double-digit growth in African (12%) and Middle Eastern markets (11%). Latin America also experienced significant growth, up 7.3%.
Cargo volumes increased by 1.5%, with the airport reporting the 20th consecutive record month.
During the course of the month, over 150,000 tonnes of cargo travelled through the UK’s biggest port.
The USA (1,659 tonnes) and Japan (682 tonnes) were among the fastest growing markets for cargo.
New routes launched by Hainan Airlines and Tianjin Airlines provided the UK’s first direct connections to the growing cities of Changsha and X’ian.
Qantas also began its first direct service to Perth from Heathrow – offering the fastest route to Australia for both UK cargo and passengers.
Heathrow CEO, John Holland-Kaye, said: “The booming growth in passenger numbers and cargo, particularly from emerging markets, underpins the urgency to secure Britain’s economic future with a third runway at Heathrow – which has now been backed by the cross-party Transport Select Committee.
"We are delighted that passengers have rated us one of the top ten airports worldwide, recognising the huge improvements in service we have made over the last few years.”