Police officers were visible around the Scottish crematorium where Johnny “Mad Dog” Adair paid his last respects to his son on Friday.
Jonathan Adair Jnr, 32, was found dead at a property in Templehill, Troon, South Ayrshire, on September 10.
The death was initially treated as unexplained by police.
However, it is understood he died from an accidental drugs overdose after being released from prison for motoring offences.
His funeral was held at Holmsford Bridge crematorium near Irvine, North Ayrshire.
More than 100 people in attendance at the short service, which lasted from roughly 1.30pm to 2pm.
The hearse carrying the coffin had white flowers spelling “dad”, “son” and “brother”.
A reporter at the scene for the Press Association said some police officers could be spotted in the area as the gathering was getting underway.
No obvious loyalist related trappings were visible from outside the service.
Ex-UDA commander Adair Snr had been quoted in the press on Friday as saying: “I just want to bury my son. I want to bury him with dignity and in peace.
“The support I have had from back home has been overwhelming.
“If a few individuals are trying to stop people attending [the funeral], it’s because they are afraid of me.
“They are afraid of me regrouping and coming after them.”
The funeral passed without incident.
Adair Snr was a leading figure in the Belfast UDA, and had been jailed in 1995 for directing terrorism.
He commanded a group in the lower Shankill area which was heavily involved in internal loyalist feuding in the late 1990s and into the new millennium, and he was forced to move to the UK mainland.
The UDA, in which he was a significant figure, murdered more than 400 people from 1970 until the time of his exile in 2003.
Echoing his father’s “Mad Dog” nickname, Jonathan Jnr was often referred to as “Mad Pup”.
He had been convicted over a decade ago of selling heroin.
Last December, the Scottish newspaper the Daily Record said he had been jailed for flouting a driving ban.
A year before that, it reported that he had been jailed for “running amok” in a flat after someone refused to sell him cannabis.
In 2002, then18, he had been shot in the legs in what was reportedly a punishment for anti-social behaviour.