Packing up the bottles of Sancerre and the tropical aquarium figured to be a cinch. But how do you transplant atmosphere? That’s the question that faced Johnny’s Half Shell when it moved to Capitol Hill from Dupont Circle. Devotees wondered if the tiny hangout—and its homespun conviviality—would get swallowed up by the sprawling space that until recently housed La Colline, one of the city’s last Old World French dining rooms.

The fears turn out to be mostly unfounded. Ann Cashion and partner John Fulchino have jazzed up the restaurant’s new home, tucked into the C-Span building (400 N. Capitol St., NW; 202-737-0400), with familiar touches: buttery yellow walls, a big-band soundtrack, and a heavy marble bar. And though there are lots more suits in the crowd, the feeling’s still easy. Only the tables in the dining rooms off the bar area, which double as private spaces, feel distant from the fun.

Renditions of Chesapeake and Gulf Coast seafood such as broiled crab cakes and fried oysters with relish remain the kitchen’s focus. But it’s worth seeking out a few more-sophisticated plates, which show a sure hand with vegetables. A slice of halibut gets a generous handful of beautifully seasoned chanterelles. Smoky grilled squid arrives atop a tart, wilted arugula salad. And even better than a shellful of crab imperial is the salad of haricots vert and heirloom tomato served alongside.

More welcome changes pop up at the end of the meal. Gone are the tired slices of lemon chess pie drizzled with raspberry coulis. In their place are slices of cloud-light coconut cake hit with passion-fruit gelee, and one of the town’s best renditions of butter pecan ice cream.

The Capitol dome shines in the background, a reminder of the new, more serious-minded neighbors who come here. But Johnny’s still feels like home.