Bitter political battles over the move have died down since a court late last month overthrew a legal challenge to the switch, and the country has pulled together in a bid to ensure a smooth changeover.
Thousands in this devout Christian nation went to church Sunday, praying for a changeover "free of injury and, heaven forbid, death", an editorial in the Samoa Observer newspaper said.
"All of those who have the safety of our people, and especially our children, in their hearts will echo those prayers by asking the Almighty to calm our tempers and reduce our speed from tomorrow."
Road signs have been changed throughout the country and road works carried out in an attempt to ease the changeover's impact on narrow, potholed country roads fringed by high vegetation.
The government of Prime Minister Tuilaepa Sailele Malielegaoi has called a two day national holiday from Monday and alcohol sales will be banned for three days to help prevent chaos.
In case things go badly, Samoa's Red Cross has been carrying out a blood donation campaign.
The switch officially takes place at 6 am Monday (1700 GMT) but it will not simply be a matter of drivers swerving from the right to the left on the hour.
A radio announcement at 10 minutes to the hour will order all traffic to stop. At 6 am, cars will move to the other side of the road and will be cleared to resume travelling 10 minutes later.
The speed limit has been cut from 35 miles an hour (56 kilometres an hour) to 25 miles an hour (40 kilometres an hour) while speed humps have been installed in many busy areas to reduce speed even further.
Tuilaepa says changing sides to be in line with Australia and New Zealand means some of the 170,000 Samoans living in those countries, which already drive on the left, will be able to send used cars home to their relatives.
Cars would become cheaper as a result and more people in rural areas could get vehicles to help develop their land, he argues.
Opponents of the switch, including the People Against Switching Sides (PASS) movement, had argued Samoans were inadequately prepared for the switch and necessary road improvements had not been carried out.
Bus companies have threatened to go on strike from Monday because the government refused to pay the cost of changing the exit doors to the opposite side of their vehicles.