“I’m looking forward to working with the current group of goalkeepers and the wider squad, having worked with several of the players previously, and I hope my experience will be able to help bring success to the team,” Margetson said.
Margetson replaces Tony Roberts as Wales goalkeeper coach.
His return means Bellamy’s backroom team is complete, following the appointments of Andrew Crofts, James Rowberry, Piet Cremers and Ryland Morgans.
“When I looked at the group of new coaching staff, there’s a lot of experience of high-level club football but not of international football, which Martyn brings with him,” Bellamy said.
“The experience isn’t only of international football, but of reaching the final stages of tournament football. That experience and knowledge will be a huge benefit and getting him involved was a no-brainer.”
Wales play their first game under Bellamy on Friday, 6 September, when Turkey come to the Cardiff City Stadium in the Nations League.
Bellamy was named Wales head coach in July following the departure of Rob Page in June.