The Blackrock College Club man was picked in the Leinster team by coach Declan Kidney and repaid this faith by playing consistently well in all four games and ending up as top try scorer for the month. The Player of the Month awards will continue throughout the season, with each winnerreceiving 500.
Brown had a try disallowed in Leinster's first Celtic League fixture against Cardiff.
This was followed by a 17- 15 win over Munster in Donnybrook with Brown showing great pace before stepping inside Christian Cullen to score a sensational try after 14 minutes.
Things got even better for Brown as he scored a hat trick in the next game against the Borders in a 50 - 13 win in Donnybrook, underlining the rich form he had shown throughout September.
Ronan Beirne, Guinness Brand Manager said, "We are delighted to continue our sponsorship of the Celtic League and the player of the month awards again for the 2004/2005 season. This year's competition has been of an even higher standard then last year, which speaks volumes for the talent of Gary Brown. He has had a sensational start to the Celtic League and we wish him all the best for the remainder of the season."