Passengers left the plane shortly after the incident and will have to take another flight to Kuala Lumpur.
One passenger reported that the man had yelled "I've got a bomb and I'm going to fucking blow the plane up".
After they were allowed to deboard the plane, passengers were interviewed on the tarmac and were made to wait for several additional hours at the airport.
Passengers with critical onward connections have been allocated seats on Malaysia Airlines' earlier flight, MH148 departing Melbourne at 13:55.
Around 11 passengers helped tackle the man at the back of the plane, and the aircraft immediately turning back for Melbourne Airport after the man had been restrained, according to multiple media reports.
While passengers suggested he was armed with a "detonator". The Transport Minister said the man appeared to be drunk.More news: United States lawmaker, others in hospital after shooting at baseball practice
No-one is believed to have been injured.
Flight MH128 was only a few minutes into a flight from Melbourne to Kuala Lumpur, Malaysia, late Wednesday when a 25-year-old Australian man attempted to enter the cockpit clutching an electronic device and created panic, Police Superintendent Tony Langdon and passengers said.
The airline stressed in a statement that the flight had not at any point been hijacked.
Arif Chaudhery, a passenger on board MH128, told Reuters that about 30 minutes into the flight a male passenger attacked a female member of the cabin crew who screamed out for help.
Malaysia Airlines said it would be investigating the incident with Australian authorities.
"Safety and security are of utmost priority to Malaysia Airlines", it said in a statement. The airline wishes to apologize for the inconvenience caused.More news: Fed raises rates and outlines balance sheet reduction plan
Australian authorities have started an investigation and passengers are being interviewed about the incident. "They will be offered on the next available flight or on other carriers".
The Airbus A330 then landed safely at Terminal 2.
Victoria Police officers arrived at Tullamarine airport at 11:55pm with the Special Operations Group and Critical Incident Response Team arriving at 12:23 pm.
Victoria state police said the man allegedly threatened the safety of passengers and staff.
"He was certainly at the cockpit door, seeking entry to the door, holding this device", he said.
"Counter-terrorism response and protocols kicked in. for us that meant having the plane isolated, and as soon as practicable, getting the passengers off the plane safely and dealing with the offender", Ashton said.More news: Uber loses another top executive Emil Michael
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