Six posters depicting offensive images and other hate and sexist material were found around the Queenstown Islamic Centre in Gorge Rd Retail Centre.
Worshipper Philippe Saint-Pere, who also teaches at the Islamic centre, said the posters were shocking.
"It shows how badly people need to understand what Islam is really all about."
He said when the masjid opened two weeks ago, an event was held for non-Muslims to ask questions about the faith, and around 60 people attended.
Mr Saint-Pere said while he understood the importance of freedom of expression, that did not mean freedom to slander.
Southern district commander Superintendent Paul Basham said police were working with the centre.
"Police are taking this matter seriously, as we do all reports of hate speech or behaviour that causes concern to our communities."
Officers carried out door-to-door inquiries yesterday morning.
Some posters were still visible on power poles and other areas of the centre car park.
Southern Hospitality employee Ben Bootsma said it was horrible to be confronted by the posters when he arrived at work.
"It was stuff we don’t want to see in this country ... We need to stop it."
Nearby, Bradley and Cook Electrical office manager Jo Emanuel said it was disappointing and Muslims should feel welcome in Queenstown.
One of the posters seen at Gorge Rd was also seen in Stanley St last week, while the same message was written in chalk on a Christchurch mosque two weeks ago.
Police said at the time it had spoken to a 36-year-old Christchurch man "in relation to a number of chalk messages written on footpaths throughout Christchurch including Al Noor Mosque, Linwood Mosque and several police stations".
