"Star Trek" icon William Shatner, meanwhile, has been named host of the April 1st gala, to be broadcast on CTV.
The choice marks a sharp generational shift from last year, when Toronto rapper Drake received strong reviews for showcasing his comedic side during his turn as MC.
"William Shatner is a Canadian hero, and with his love for music, the stage, and entertaining as a whole, it's sure to be an incredible show!" said Melanie Berry, who is president and CEO of the Canadian Academy of Recording Arts and Sciences, the group that administers the Junos.
Shatner hosted the Genie Awards - which honour the best in Canadian film - last year in Ottawa.
The multiple nods for Vancouver-based Mangan come as somewhat of a surprise.
In addition to nominations for songwriter of the year, alternative album of the year and video of the year, he'll face off in the new artist category against Alyssa Reid, Diamond Rings, JRDN and Lindi Ortega.
Competing for group of the year are: Arkells, Down With Webster, Hedley, Nickelback and the Sam Roberts Band.
Feist, Deadmau5, Nickelback and City & Colour are among the scheduled performers.
The Juno Awards have rotated to various cities around Canada for the last decade to great success. They returned to Toronto last year to celebrate their 40th anniversary.
Tickets to this year's show go on sale Friday.
To view a complete list of 2012 JUNO Award nominees, as well as their bios and hometown information, go to www.junoawards.ca.