Its suppliers have told staff they might not get any next week and Mr Katsoulis is particularly worried because next Tuesday is World Sushi Day.
"World Sushi Day without avocado is like Christmas without turkey."
St Pierre's two top-selling sushi varieties have avocado in them.
The shortage has also driven up the price at supermarkets - New World in New Lynn is selling avocados for $4.99 each.
New Zealand Avocado spokeswoman Midge Munro said irregular harvests were a characteristic of the avocado tree.
"Avocados are not picked in large quantities until around September when they are mature.
"Large-scale harvest usually finishes in April," she said.
Picking for the next season is expected to start within the next month. As supply volumes increased, prices were expected to move accordingly.