Gabriela Isler was crowned at a sprawling exhibition hall on Moscow's outskirts. Patricia Rodrigues of Spain was the runner-up. The panel of judges was led by musician Steven Tyler.
Earlier this week Ms Cassidy told the Bay of Plenty Times she had formed friendships with other contestants, including her roommate Miss Israel and Misses Sri Lanka, Guyana and Korea.
"The other contestants are all really beautiful girls with lovely personalities.
"I was blown away by how these girls treat each other, everyone has respect for each other."
The Bay of Plenty Times could not contact Ms Cassidy before this publication went to print but her mother Michelle Betts said she was very proud of how far her daughter got in the international competition.
"The whole experience has been awesome for her.
"She did very well and I couldn't be prouder."
Ms Betts said Ms Cassidy was due back in New Zealand this week.
"She has a couple of long flights ahead of her but I am hoping I will be able to see her next weekend."