The display of the new bill in Ottawa follows the release of similar $100 bills that went into circulation in November and $50 bills introduced in March.
Minister of Finance Jim Flaherty and Bank Governor Mark Carney said apart from features much more difficult to reproduce, the bills are cheaper to produce than paper-cloth bills and will last at least twice as long.
The bills feature such security measures as transparent windows, invisible numbers and metallic portraits, the bank said in a release.
The bank said $20 bills account for more than 50 percent of all bills in circulation.
The new notes will begin circulating in November and the remaining $10 and $5 denominations will be replaced with polymer versions by the end of 2013, the release said.
Canada uses coins for $1 and $2 denominations and is scheduled to stop producing pennies later this year.