Donations are flowing into the SPCA after the tragic death of Jacinda Ardern's adopted cat, Paddles.

News broke on Wednesday morning that the 'First Cat of New Zealand' was hit by a car in the Auckland suburb of Point Chevalier the night before.

Both the Prime Minister and a Twitter account in Paddles' name posted tributes to the cat, thanking the SPCA, where the feline with opposable thumbs was adopted.

Since then, mourners across New Zealand have given "several donations… in memory of Paddles", an SPCA spokesperson says.

"We are thankful that Jacinda and [partner Clarke Gayford] asked the public to donate to us in Paddles' memory. These donations will go towards helping rescue other kittens like Paddles."

SPCA chief executive Andrea Midgen says everyone's thoughts are with Ms Ardern and Mr Gayford.

"We hope that they seek comfort in knowing that in adopting Paddles, they gave her a life filled with happiness and love.

"To anyone who has ever lost a pet, you'll know how sad we feel," the Prime Minister said on Facebook on Wednesday morning.