Zeta-Jones, Douglas and her parents, Patricia and David Jones, spent 90 minutes Friday touring facilities at the Children's Hospital for Wales in Cardiff.
Four years ago, the Hollywood couple officially opened the hospital which included both treatment and play wards.
On Friday, she told reporters: "It really is an honor for me to come back when it's running."
Zeta-Jones, who was born in the Welsh city of Swansea, became a patron of the Noah's Ark Appeal for a Welsh children's hospital in 2000. The appeal is now working to raise 7 million pounds ($10.8 million) to complete the second phase of the project.