Streetcar track replacement work began Monday in anticipation of the arrival new low-floor streetcars in 2014.
TTC spokesman Brad Ross said the unique nature of the busy downtown intersection is the reason for the lengthy closure.
"It's one of the few intersection that we have that allows for streetcars to go in any direction in terms of turning. There's a lot of switches in that intersection. All of that track has to be pulled out, which is of course embedded in concrete," he said.
"It's a lot of work that has to be done and it's a lot more efficient to get it done in one chunk of time rather than over a period of months."
Streetcars along Queen Street will be diverted during the closure.
A complete list of diversions is listed on the TTC website. Commuters are being advised now to use Dundas, Richmond, Adelaide and King streets as alternates.
Bathurst Street and University Avenue are being recommended as alternative north-south routes.
Streetcars have already been replaced by buses on Spadina. They will also be diverted to avoid the construction zone.
The intersection is scheduled to reopen on July 23.