Charlottetown has the third highest vacancy rate in the country, with almost nine per cent of available rental units sitting empty this April.
The CMHC report noted this is the second year in a row that Charlottetown vacancies have been this high.
"In 2014, the vacancy rate remained relatively unchanged at 8.5 per cent, which is above the recent long-term average," said Jason Beaton, CMHC's Market Analyst for Prince Edward Island.
"The completion of more than 150 purpose-built rental units last year and falling international immigration kept the vacancy rate elevated in Charlottetown."
In 2013, rental costs had remained steady despite the high vacancy rate, but rental costs are down this year.
The average monthly cost for a two-bedroom unit in Charlottetown is down two per cent to $814.
In Summerside, the vacancy rate jumped five percentage points, rising from two to seven per cent.
Despite that, average rents have climbed seven per cent, from $697 a month to $744 for a two-bedroom unit.
Moncton has the highest vacancy rate in the country at almost 11 per cent, and Saint John is a close second at 10 per cent.