Ledley was a key player in Wales’s 3-0 victory over Russia at the European Championship.
The win for Chris Coleman’s side at Stadium Municipal in Toulouse means that they have progressed to the last-16 stage of the Euro 2016 finals as Group B winners ahead of England.
Henderson, who has been at Celtic his entire professional football career so far and is a Scotland Under-21 international, was following the match.
The Celtic midfielder was impressed with the performance of Crystal Palace midfielder Ledley, who was on the books of the Bhoys from 2010 until 2014.
Ledley started the game for Wales against Russia and played for 76 minutes.
The former Celtic midfielder had a pass accuracy of 92%, won both of the tackles he attempted, and made three interceptions.
In 19 Premier League appearances for Palace during the 2015-16 season, Ledley scored one goal, created three chances, had a pass accuracy of 80% and a shot accuracy of 50%, and won 12 headers, two dribbles and 11 tackles.