The legislation has cleared the lower house and is expected to reach a final vote in the upper house on Wednesday, after members consider more than 100 late amendments to the bill.
Debate will begin before midday is expected to continue until midnight.
Independent MP for Sydney and the architect of the legislation, Alex Greenwich, is hopeful the voluntary assisted dying bill will finally pass after years of campaigning.
"Today is a really important day in NSW," he told Sydney radio 2GB.
"We hope that by the end of it people with cruel and advanced terminal illnesses will have the same end of life care offerings as people in every other state."
He hoped the final debate would be "respectful and robust" before the bill is finally passed, making NSW the last state to allow voluntary assisted dying.
Some of the amendments put forward - if accepted - would enable residential aged care facilities and hospitals to ban their residents or patients from accessing voluntary assisted dying.
"This bill isn't about those institutions, it's about people with advanced, cruel, terminal illnesses who want to be able to die with dignity, with a bit of control and in a compassionate way," Mr Greenwich said.
A poll conducted by Go Gentle Australia has found three quarters of NSW residents support dying people having access to all legal medical treatment options within their own home, including aged care facilities.
Similarly, 74.1 per cent said terminally ill people living in aged care should not be blocked from accessing voluntary assisted dying by their provider.
If the bill passes on Wednesday unamended, voluntary assisted dying is likely to become available to terminally ill people in NSW in 18 months.
If the bill is amended it will have to return to the lower house on Thursday for approval.
Opponents of the bill, including Labor MLC Greg Donnelly and Christian conservative MP Fred Nile, put forward more than 100 amendments this week, Nine Newspapers reported.
NSW Opposition Leader Chris Minns said he was not aware of what the amendments moved by Mr Donnelly were, but did not agree it was a delaying tactic.
"It's hard for me to divine right here right now whether the 200 amendments solemnly felt designed to make the bill stronger, put in safeguards that are appropriate in NSW, or they're a delaying tactic," Mr Minns said.
"The best way for the NSW parliament to deal with a large number of amendments is to sit continuously until the legislation is passed."
