Originally Posted by Symmetre

To add to the above info, OP might consider two additional things:

1. Do you have a NEXUS card? If so, then the 1:15 connection is possible since NEXUS *normally* expedites your passage through customs. If you do not have NEXUS, or if for some reason NEXUS is unavailable at the time, then getting through the regular customs line *normally* takes a bit longer ... exactly how much so depends on how many other international flights arrive just before yours does, and how many other people are already in the line ahead of you. Checking the Toronto Airport website arrivals/departures page should give you some idea of how busy it will be at that time of day.

2. How does that Punta Cana flight perform in terms of operating on time? If your flight from Punta Cana arrives in Toronto 20 minutes late, for example, then obviously that will reduce your odds of making the connection. Some routes are prone to chronic delays ... you might want to see what you can find out on a resource like Flight Aware (Google it) which will let you see a history of different flights between various cities so you can spot any pattern of consistent delays. If your flight shows a history of consistently running late, then that should be a factor in your decision.

I should add that if you are delayed and have checked luggage, then there is the chance that you could still make a tight connection but your bags don't. So, there is a potential inconvenience factor in Ottawa that plays into it as well.

IF your Punta Cana flight is on time, and you have NEXUS, I'd say you're probably fine. But if you see that northbound flight has a history of running behind schedule ... or if you don't have NEXUS .... then it's inherently riskier.

Personally, I would do a bit of research and barring any clear red flags, I'd most likely book the short connection and hope for the best. If things look sketchy, then save the grief, book the longer layover and plan on having dinner at the airport while you're in YYZ.

Either way, good luck.