Parish, who is assistant to Ricky Stuart at Parramatta, takes over from St George Illawarra coach Steve Price following his departure by mutual consent.
"I feel both honoured and privileged to have been appointed as the head coach of Toa Samoa," Parish said.
"I hope that through my experience working in the NRL, State of Origin and with the Indigenous All Stars, I can help convert that unquestionable talent into results at the World Cup."
Samoa, who beat the United States in a friendly in Hawaii at the weekend, are in the same group as New Zealand, Papua New Guinea and France.
Samoan RL president Tagaloa Faafouina said: "We don't expect Mattie to do miracles but we believe he will be a great asset to bring benefits to our team as we are on the look out for accomplishments."
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- Ricky Stuart
- Indigenous All Stars