With the Mediterranean directly outside the harbour, seafood naturally belongs on a Toulon food itinerary. But rather than looking for one supposedly perfect restaurant, I would start by understanding what is local and seasonal.
Fish markets and restaurant menus can change with the catch, which is exactly how coastal food should work. Depending on the season and restaurant, you may encounter Mediterranean fish, mussels, shellfish and dishes influenced by wider Provençal traditions.
Look at the whole menu
Freshness matters more than choosing the most famous species. Ask what is local, look at daily suggestions and do not assume that the longest seafood menu automatically means the best experience.
The harbour is an obvious place to eat, but restaurants elsewhere in central Toulon and Mourillon can be equally interesting.
Try Provençal flavours
Garlic, olive oil, herbs and tomatoes appear repeatedly in the cooking of southern France. Seafood may be grilled simply or become part of richer soups and stews.
If you enjoy markets, visit Cours Lafayette earlier in the day before having seafood later. Seeing local produce first gives the meal more context.
Toulon does not need to compete with glamorous Riviera destinations on presentation. Sitting near the Mediterranean with a plate of well-prepared fish is already one of the simplest pleasures the city can offer.