The 36-year-old is set to make his 632nd appearance in the top flight on Saturday as the Baggies prepare to face West Ham United.
He made his Premier League debut for Aston Villa in May 1998 and returned to the Midlands this summer, joining Albion from Everton, and Pulis says he has been a great servant.
“It is a wonderful achievement, we have only just had him a few weeks,” said Pulis.
“I have always rated him as a player but you don’t realise how good he is until you actually work with him.”
“Managers who have had him for longer periods are better versed talking about Gareth than myself.”
Barry reportedly cost West Brom just £800,000 as he made the switch from Everton in the summer.
A goal apiece from James Tomkins and Luka Milivojevic handed Crystal Palace a crucial 2-0 win over Huddersfield at the John Smith's Stadium on Saturday evening.
Manchester United bounced back from their Champions League exit as they beat Brighton 2-0 at Old Trafford on Saturday night to reach the FA Cup semi-finals.
Tottenham reached the FA Cup semi-finals after they cruised to a 3-0 victory over Swansea in their quarter-final clash at the Liberty Stadium on Saturday.
Premier League basement club West Brom squandered the lead as they suffered a 2-1 defeat to Bournemouth at the Vitality Stadium on Saturday.
Chesterfield boss Jack Lester felt his side were unlucky not to claim all three points after their 1-1 draw at Cheltenham.
New Swindon manager Phil Brown revelled in his side's victory at Cambridge in his first game in charge.