They can be reserved at first but warm up quickly.

Sealyham Terriers tend to be a bit cautious around strangers, but they aren't aggressive. With proper socialization, they usually become friendly after a few meetings. One thing I've noticed is that they have a unique way of assessing new people, often sitting back and observing before deciding to approach. It's important to introduce them to various environments and people early on, so they grow up to be more confident around strangers. In my experience, patience pays off with this breed.