The midfielder, 31, who has been promoted three times from the lower-leagues and was skipper at previous club Hull City, will wear the armband for the first time in Saturday's League Two opener against Yorkshire rivals Doncaster Rovers.
On the decision to name ex-Hull, Middlesbrough and Rotherham United player Smallwood as captain, manager Mark Hughes said: “As I said when Richie signed, in him, we have not only a fantastic professional who has achieved an awful lot in the game, but a real natural leader.
“His stature and influence in the dressing room, even at this early stage of the season, has had an impact on everyone, and is there for all to see.
“He has the ability to control games from midfield, and his leadership not only off the field, but by example on it with 100 per cent. commitment, made him the obvious choice.
“We hope you (supporters) will get behind him and the rest of the players at Valley Parade this weekend, and hopefully he will be able to lead us to a successful season.”