When made with kosher fish, rice and vegetables, sushi can be kosher and delicious. But lots of sushi is not kosher. It may be made with non-kosher seafood, rice cooked in non-kosher pots, or other problematic ingredients. As such, a Jewish person may only enjoy sushi produced under reliable kosher supervision.

In many major North-American cities, you can find excellent kosher sushi available for purchase, which often includes surimi, mock crab. You can read more about why that is OK in Are Imitation, Crab, Pork, and Cheeseburgers Kosher?