I would not recommend a person walking after 9pm at night alone downtown. Remember Montreal is very diverse and there are millions of people. The more people the more your chances are for finding trouble.
Lower in town (Ontario street) is a seedier part of town. Drug-addicted prostitutes, heroin addicts etc. I would not go in the bars on this street at night as sometimes bikers blow them up. During the day, it's safer, but you can still feel and see a bit of poverty and prostitutes in a very bad shape. also, don't do like me and troll your hand on window stills as one day I almost had a seringue plucked in my hand!!
At night, I don't even think about coming here. No gangs or things like that..but it's just a bad part of town..
At night, also avoid Montreal-North (East of PIE-IX street, north of Sherbrooke street AND keep off Pascal street.) because there are gang wars.)Taxis won't even bring you there anyways...or pick you up!
Oh..and the Parc-Extention district too..
For a North America major city, Montreal is fairly safe. Obvious dark corners can be easily skiped at night, but the overhall feeling is very safe and you can usually walk alone at night in the streets and not be bother.
Canada in general is a very safe place but like everywhere else we have our crime problems.If you use your common sense you should have no problems but try to avoid the far east end of the city if possible (especially at night). Laso turning on a red light is against the law here so for your own safety and those of the crazy pedestrians please don't.
Montréal, like almost every places in Québec, is a very safe city. There's some spot you don't want to go at 3:00 am in the morning, like St-Henri or Montréal-Nord, but you dont want to go there in the day anyway because there's nothing to see except some dirty poor places with no attractions at all.
Walking through an area called the 'McGill Ghetto' is not advisable late at night for lone females or gay men. Although it is not a terrifying experience, many of my friends have had unpleasant experiences with druken frat boys. The ghetto is the area east of McGill campus up until about Park Avenue.
If I were you, I wouldn't wander in the Centre-Sud neighbourhood at night. It's pretty grim along parts of rue Ontario, especially east of avenue Papineau; the abandoned warehouses and factories were pretty disconcerting. Some of southwest Montréal isn't great at night, either, such as St-Charles and parts of Verdun.
I believe that Montreal is one of the safest big city in North America. Women could almost walk around by themselves at 3 AM without too much trouble.
Avoid unlit parking lot and city area (southeast), but if it is lit, you are probably ok. Montreal has purse snatcher, gang violence, poverty, bad neighborhood, etc...
Bottom line : act intelligently but enjoy Montreal without fear.