The accolade comes after a month in which the former Arsenal trainee Sidwell has played a central role in leading the Royals to third place.
Sidwell, a combative midfielder, contributed a lot to Reading's good performances last month, but his most important contribution of September was to head home the only goal of the game as we defeated high-flying Watford 1-0 at Vicarage Road.
Meanwhile, Portsmouth striker Rowan Vine, currently on loan at Luton Town, has been named as League One Player of the Month for September. The 22-year-old scored three times to keep the Hatters at the top of the table.
In League Two, Yeovil forward Phil Jevons scooped the division's top player award after scoring an impressive four goals in September, including a hat-trick against Oxford as the Glovers romped to a 6-1 victory.