She was formerly the world record-holder in the 200-metre long course breaststroke until Rebecca Soni beat her time by 12 hundredths of a second during the 200-metre semifinals at the 2012 Summer Olympics.

She was also a member of the Canadian team that finished seventh in the women's 4×100-metre medley relay.

Thanks to this achievement, Pierse also won the Canadian Interuniversity Sport (CIS) female athlete of the year award for 2008–09.

1/10 of a second faster than the previous world record, Rebecca Soni set at the Beijing Olympics.

Pierse brought home a bronze medal in the 200m breaststroke from these Championships; Being behind Rebecca Soni, and Leisel Jones.