Autobots and Decepticons will take over the city until August 19.
The film is creating 200 area jobs, and it is expected to pump millions of dollars into the local economy.
"We anticipate, as well as the Transformers folks, to spend a minimum of $20 million here," said Rich Moskal of the Chicago Film Office. However, it will also create a headache for drivers trying to get around in the Loop.
The filming for the movie will take place primarily in the LaSalle Street Financial District. An aerial photography unit will also be flying near the Willis Tower, East Randolph Street and Daley Plaza.
Film ambassadors in yellow T-shirts fanned out Friday to let people know what is going on and to guide people around the closures.
"We came all the way from the south suburbs to see this," said Transformers fan Jerise Ricard. "We're really excited."
A normally empty lot at Washington and Franklin was transformed into a staging area for lots of fake rubble and crushed vehicles.
"It's really cool, but it looks a lot different than in the movies," said fan Grace Lasky.
The movie will showcase some Chicago landmarks, including Trump Tower, which base-jumpers will dive off of next weekend.
Street closures:
LaSalle Street closed from Jackson Avenue to Wacker Drive
8 p.m., Friday - 6 a.m. Monday, July 12.
Washington Avenue closed from Wells to Clark and Randolph closed from Wells to Wacker 6 a.m. Saturday - 5 a.m. Monday, July 12.
Wacker will be closed between Monroe and Van Buren beginning Friday at 7 p.m. until Monday July 12 at 5 a.m.
Brief intermittent closures of intersecting streets at LaSalle Street between Jackson, Adams, Madison and Monroe avenues are to be expected as well.
The routes most likely to be impacted are those that that travel along LaSalle Street, Michigan Avenue between Randolph Street and Ohio Street and along Wacker Drive.
The movie will be filming in various places around Chicago at various times between July 10 and August 23. The city estimated the filming will brig the city $20 million and 200 jobs.
Due to the street closures, the following CTA reroutes will be in effect this weekend:
Northbound #14 Jeffery Express and #56 Milwaukee, westbound #60 Blue Island/26th and southbound #124 Navy Pier buses will travel over the regular route to Madison/Dearborn then will operate via Dearborn, Wacker then return to Madison and resume the regular route.
Southbound #14 buses will travel over the regular route to Monroe/Canal then will operate via Canal, Lake, Clark to Monroe and then resume the regular route.
Eastbound #60 and northbound #124 buses are not affected and will operate over the regular route.
Eastbound #20 Madison and southbound #56 Milwaukee buses will travel over the regular route to Washington/Franklin then will operate via Franklin, Wacker, Clark to Washington and then resume the regular route.
Westbound #20 Madison buses are not affected and will travel over the regular route.
Eastbound #126 Jackson and #130 Museum Campus buses will travel over the regular route to Jackson/Canal then will operate via Canal, Lake, Wacker, Clark, Jackson and then resume the regular route.
Westbound #126 buses will travel over the regular route to Adams/Dearborn then will operate via Dearborn, Wacker, Madison, Clinton to Adams and then resume the regular route.
Westbound #130 buses will travel over the regular route to Adams/Dearborn then will operate via Dearborn, Wacker, Madison to Clinton and then resume the regular route.
Southbound #151 Sheridan buses will travel over the regular route to Adams/Dearborn then will operate via Dearborn, Wacker to Madison, Clinton to Jackson before turning to begin northbound service.
Northbound #151 buses will depart from Jackson/Clinton and travel via Jackson, Canal, Lake, Wacker, Clark to Jackson and then resume the regular route.
