Siddle was one of four unanimous selections in the side, earning the tick of approval of every coach in the league.
Ben McDermott, Josh Philippe and Daniel Sams were the other players to receive a maximum eight votes.
Siddle, who retired from international cricket in 2019, has played a key role in the Adelaide Strikers' remarkable surge deep into the BBL finals.
The 37-year-old is poised to finish this season's leading wicket-taker, having captured 29 wickets at 17.37 before Wednesday night's challenger final against the Sydney Sixers.
The Strikers, who continue to be captained by Siddle despite the return of Test stars Travis Head and Alex Carey, have won six games in a row.
McDermott became the first player in BBL history to hit consecutive centuries during another productive campaign for the Hobart Hurricanes, scoring a league-best 577 runs at 48.08.
Sixers wicketkeeper Philippe was the obvious choice to take the gloves, having helped himself to 429 runs at 33 while opening the batting for the defending champions.
Sydney Thunder's Sams underlined his allrounder credentials with an incredible knock of 98 not out, while he finished the season with 19 wickets at 24.57.
Strikers spinner Rashid Khan, Sixers allrounder Hayden Kerr and Perth Scorchers veteran Andrew Tye round out the team's attack.
Englishman Joe Clarke is Melbourne Stars' sole representative in the XI, while Mitch Marsh, Matt Short and Moises Henriques earned spots in what would be a powerful top six.
Sean Abbott and Jason Sangha were named X-factor substitutes.
"This is one of the most exciting team of the tournament line-ups in BBL history, featuring a combination of World Cup winners, seasoned BBL veterans, breakout stars and history-makers in our competition," BBL consultant Trent Woodhill said.
"We congratulate all players selected and thank the eight head coaches for their careful consideration in selecting this side."
BBL TEAM OF THE TOURNAMENT: Ben McDermott, Josh Philippe (wk), Joe Clarke, Mitch Marsh, Matt Short, Moises Henriques, Daniel Sams, Rashid Khan, Hayden Kerr, Andrew Tye, Peter Siddle (capt). X-factor substitutes: Sean Abbott, Jason Sangha.
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