Legislative Council members supported the End of Life Choices (Voluntary Assisted Dying) Bill late on Tuesday night, approving amendments from the lower house.

The lower house had backed the bill in a 16-6 vote in early March, with Premier Peter Gutwein among a handful of Liberals to support it.

The upper house, where the legislation was introduced by Independent Mike Gaffney, had already passed the bill unanimously late last year.

"It will give those Tasmanians who are suffering intolerably, who are eligible the right to choose (to end their life)," Mr Gaffney said.

The new laws are expected to become active in 18 months.

Sisters Jacqui and Natalie Gray, who founded advocacy group Your Choice Tasmania after the death of their mother, said the new laws were "the legacy of all of our loved ones that died without this compassionate end-of-life choice".

"The stories of their courageous battles have helped change the invisible face of terminal suffering and the concerning dark conversations that have gone on needlessly in the absence of this law," they wrote in a Facebook post.

It is the fourth time proposed euthanasia laws have come before Tasmania's parliament. Similar laws exist in Western Australia and Victoria.

"We extend our deepest gratitude to all who have poured their heart and soul into achieving this reform," Greens leader Cassy O'Connor said in a statement.

Under the laws, people over 18 with an advanced, incurable, irreversible condition expected to cause death within six months can end their lives.

They must have decision-making capacity and be acting voluntarily and can opt out of the procedure at any time.

The reform was backed by a petition containing 13,000 signatures which was tabled in parliament.

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Australian Associated Press