The arrest of the man, who was stopped by police at Brisbane airport, brings the number of people held in the investigation to eight.
Australia's attorney general said the man was a 27-year-old doctor - like two others arrested - who was trying to leave the country on a one-way ticket.
Australian police were acting on information from the UK authorities.
Attorney General Philip Ruddock said police had executed search warrants at the Gold Coast Hospital in Southport, eastern Queensland - where the man worked as a registrar - as well as at a number of locations across the state.
The man is a resident, but not a citizen, of Australia, he added.
The Metropolitan Police are in charge of the investigation into the bombings.
Meanwhile, it is understood a suspect held in Scotland will be transferred to the UK capital.
Iraqi Bilal Abdulla will be taken to Paddington Green police station where another doctor is also being quizzed.
Dr Mohammed Asha, 26, who was brought up in Jordan and worked as a junior doctor at the Royal Shrewsbury Hospital and the Princess Royal Hospital in Telford, was arrested on the M6 in Cheshire on Saturday night along with a 27-year-old woman thought to be his wife.
Strathclyde Police said two men aged 28 and 25 arrested on Sunday were held at residences of the Royal Alexandra Hospital in Paisley.
The other man detained at Glasgow airport with Dr Abdulla had severe burns and remains in a critical condition, and under armed police guard, at the Royal Alexandra.
The hospital is where Dr Abdullah was employed as a locum.
Police have been carrying out searches of premises and vehicles within the grounds of the hospital and controlled explosions have taken place.
But Chief Superintendent Johnny Gwynne reassured local people there has been no indication of a threat to the hospital - which remains open - and said the actions taken were "purely precautionary".
The fifth person detained, a 26-year-old man, was arrested in Liverpool on Sunday.
Warrants have been issued which allow police to further detain the three people arrested in England until Saturday.
Dr Asha was described by family and university colleagues in Jordan as a "brilliant" physician who had not been involved with extremist organisations.
According to his father Jamil, he obtained a medical degree in Jordan in 2004 and came to the UK in the same year to gain a specialisation in neurology.
Dr Abdulla is said to have qualified in Baghdad in 2004 and first registered as a doctor in the UK in 2006.
Detectives are linking the failed bombings, and the UK's terror alert system has been raised to its highest level - critical.
Security has been stepped up with extra police patrols and vehicle searches taking place at airports and transport hubs.
In a Commons statement, Home Secretary Jacqui Smith said the country would not be "intimidated" by "those who wish to destroy our way of life and our freedoms".
She said 19 locations have been searched by police investigating the attacks.
These include properties in Houston, near Glasgow; Merseyside and Staffordshire.
Detectives are trying to trace the movements of the green Jeep Cherokee - registration L808 RDT - loaded with gas cylinders, which crashed into the doors of Glasgow airport's main terminal and burst into flames on Saturday afternoon.
The attempted attack came a day after two Mercedes containing petrol, gas cylinders and nails were found outside a nightclub in London's Haymarket and in a nearby street.