The march includes representatives from New Zealand - including a group from the police force - and the Otago University Samoan Students Association.
Auckland woman Tauiliili Tivoli said it was a privilege to witness events today.
"I'm so honoured to be here today,'' she said.
"I can't believe how far our beloved country has come and here we are, standing here today. I am so happy that I decided to come here for Independence.''
People began gathering in the city's capital from as early as 1am. Parking has been prohibited from the main area.
Meanwhile Samoa's head of state has made a surprise announcement during speeches to mark the anniversary.
35 prisoners have been given amnesty due to the independent celebrations.
And Barack Obama has congratulated Samoa on marking 50 years of independence.
The president says the US is pleased to be able to call Samoa not just a neighbour, but a valued friend and partner.
He says both countries have worked together to address pressing issues, and looks forward to building on that in the years ahead.