The year 13 pupils were jointly recognised as the best individual speakers at the two-day event, which attracted 25 teams from schools throughout the southern region.
The pair will now represent the region at the national finals in Wellington from July 3-6.
Suzannah has attended three Muna competitions and said this year she spoke a lot more.
Alex also attended last year and said the competition was great for challenging himself, developing critical thinking and researching other countries' positions on issues.
Both were part of three- or four-strong teams from their school, with Alex's team representing New Zealand and Suzannah's team the voice of Brazil.
Both pupils are members of Mt Aspiring College's Rutherford extension programme for year 10-13 pupils in English and social studies.
They also take calculus, biology, physics, chemistry and literature, while Suzannah is learning Spanish and Alex studies painting.
Logan Park High School of Dunedin, representing France, won an award for best team.
