Goodall ate a final meal of fish and chips and cheesecake before dying.
Around midday, an IV was placed into Goodall's arm, allowing him to turn a wheel to let the lethal drugs to flow into his bloodstream, according to Exit International, an Australian nonprofit that advocates for the legalisation of euthanasia.
The British-born scientist, described by Exit International as its first member, said this week that he had been contemplating the idea of suicide for about 20 years, but only started thinking about it for himself after his quality of life deteriorated over the last year.
A group named Exit International helped Goodall find a suitable place to commit assisted suicide.
"There's not going to be many people who have either the ability or the money or the willingness to go through what is quite a long and hard journey", Dr Nitschke said from Switzerland. In traveling to Switzerland, he said he hoped his example would lead to debate and give more people the option of physician-assisted suicide.
While increasingly feeble and unable to live as he once did, Goodall is not sick.
"Up to the age of 90 I was enjoying life, but not now", he said. "Life stopped being enjoyable five or 10 years ago", he said, in part because of his failing mobility and eyesight.
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"I greatly regret having reached that age", he said upon reaching his 104th birthday.
"That which I would like is to get different states to follow Switzerland's guide and make them facilities available for all clients, should they satisfy certain demands, and also certain requirements perhaps not only of age, but instead of mental capacity".
The organisation's statement added that Goodall "has requested that his body be donated to medicine and, if not, that his ashes be sprinkled locally".
Goodall said he had no doubts over his chosen course of action and was grateful for the opportunity to "come to an end gracefully".
"I'm looking forward to it", he said of his imminent death.
He had attempted suicide three times, but Australian medical professionals saved him.
In 2016, aged 102, he won a battle to keep working on campus at Perth's Edith Cowan University, where he was an unpaid honorary research associate. After an uproar and support from scientists globally, the decision was reversed.
Dr Goodall told reporters on Wednesday: "One should be free to choose the death, when death is at an appropriate time".