Mrs Dewani, 28, died after the car she was travelling in with her husband, Shrien, 31, was hijacked in Cape Town.
The vigils are to be held on 13 November in Bristol, London, Cape Town and also Sweden where she was born.
Taxi driver Zola Tongo from Bothasig, Cape Town, has been jailed for 18 years for murder, kidnapping, robbery with aggravating circumstances and perverting the course of justice after agreeing a plea bargain.
Mr Dewani, from Bristol, faces charges of murder, conspiracy to commit murder, robbery with aggravating circumstances and obstructing the administration of justice.
Mr Dewani's extradition was backed by Home Secretary Theresa May after a judge approved the move in August.
An appeal has been lodged with the High Court.
Mrs Dewani's uncle, Manoj Panchmatia, who helped organise the vigils, said it had been "a very difficult year for the family".
Lighting a candle
Mr Panchmatia said the idea had come from users of Facebook who wanted to do "something special".
"In addition to the four centres there are hundreds and hundreds of emails we have from people who cannot make it to the vigils who will be lighting a candle."
The vigils, including one in Harrow, north London, where Mrs Dewani lived with relatives before getting married, are scheduled for 17:30 GMT.
Two other men, Mziwamadoda Qwabe, 25, and Xolile Mngeni, 23, are also charged with murder, as well as kidnapping and robbery with aggravating circumstances and will go on trial at the Western Cape High Court next year.