Yes, and it is one of the highest-return small jobs in an older house. The rim joist is a continuous band of uninsulated framing at the top of the foundation, and closed-cell foam seals and insulates it in one pass.
More detail
The rim joist, sometimes called the band joist, is the framing member that sits on top of the foundation wall and closes the end of every floor joist. In most houses built before the mid-1990s it is bare wood with nothing on it, and it runs the entire perimeter of the house. Why it punches above its size. It is at the bottom of the stack effect, so it is where replacement air enters all winter. It is a direct connection between conditioned basement air and outdoors across a continuous band. And because it is in the basement rather than in an attic, the air that comes through it is the air the household breathes. Why foam rather than batts. The traditional treatment is fiberglass stuffed into each bay, which does not seal, allows warm humid interior air to reach the cold rim, and condenses moisture against wood that then cannot dry. That assembly rots. Closed-cell foam applied directly to the rim adheres, seals, and acts as its own vapor retarder, which is the reason it is the standard specification here. Scope and effort. It is a small material quantity, usually a few hundred board feet for a typical house, and the work is done from inside the basement or crawl with no disruption upstairs. It is frequently combined with crawl space or basement work already scheduled, which is the cheapest way to buy it. What to check first. Any existing moisture or rot at the rim gets addressed before it is covered. And where a rim bay contains a dryer vent, a gas line, or a sill plate showing insect damage, that gets resolved rather than encapsulated. In Climate Zone 5A the code specifies rim joist treatment alongside the wall assembly, and the retrofit is usually straightforward to bring to that level.