Supermarkets, stores, banks and government buildings have been repainted red and blue, and other buildings have national flags flying from their rooftops.
At Mulinu'u - where most of the main events will be held - island huts have been built to sell food.
At the nearby market, hundreds of stalls are selling souvenir T-shirts, lavalava and jewellery.
Stallholder Rosa Tanielu, of Fusi, said she had only 114 left of the 500 T-shirts she ordered in the reggae colours of red, green and yellow.
"Lots of them said they were wearing them to the UB40 concert. I bought so many shirts, thinking it would be more than enough - but it's not," Mrs Tanielu said.
Sidney and Amelia Ene, from Pakuranga, were in Apia yesterday taking in the sights.
They are among thousands of overseas Samoans expected to travel to their motherland this week for the 50th anniversary celebrations.
The couple said they were excited to be in Samoa at an important time of the country's history.
Mr Ene said: "This is my second time here in Samoa and the first time I've been here for an Independence [Day].
"It's awesome to see everything and to be here with family."
MARKING THE MILESTONE
Today: Official opening ceremony.
Friday: Flag-raising ceremony, march, cultural performances, fireworks display, UB40 concert.
Saturday: Float parade, arts and crafts exhibition, sports, Independence ball.
Sunday: Candlelight thanksgiving service, gospel concert.
Monday: Marching girls and brass competition, variety concert, Chinese acrobat show.
Tuesday: Traditional outrigger regatta, launch of official book celebrating 50 years' independence, lowering of the flag, closing ceremony.
