The short answer is yes—these outdoor benches are treated and sanded smooth, so splinters are not something you should have to deal with on a well-made bench. I totally understand the worry, though, because rough or cheaply finished wood can be miserable.
Quality wooden outdoor benches are usually built from kiln-dried hardwoods like teak, acacia, eucalyptus, or oak. The drying process stabilizes the wood, and then the seat slats and armrests are machine-sanded smooth—often to at least 120 grit—so the surface feels soft to the touch. After sanding, the bench is treated with a clear outdoor sealer, decking oil, or weather-resistant polyurethane. That treatment seals the grain, reduces moisture damage, and helps prevent raised fibers from turning into splinters.
If you are shopping and want extra peace of mind, look for terms like “sanded smooth,” “splinter-free finish,” “rounded edges,” or “pre-oiled.” Avoid rough-sawn or unfinished timber unless you are happy to sand and seal it yourself. Metal benches, recycled plastic benches, and poly lumber benches are naturally splinter-free and require almost no maintenance.
When your bench arrives, do a quick hand test. Run your palm across the seat, armrests, and especially the underside edges where hands tend to grip. If anything feels fuzzy or sharp, a light pass with fine-grit sandpaper and a fresh coat of outdoor wood sealer will take care of it before it ever becomes a problem.