The crossover starts on Chicago Fire S13E11 In the Trenches (I) and Chicago Med S10E11 In the Trenches (II).

NBC’s One Chicago is airing its first crossover in five years tonight. Here’s how to watch the epic event featuring "Chicago ...

There's a shift in show order for the crossover event. “Chicago Fire” will air first at 8 p.m., followed by “ Chicago Med “ at 9 p.m., with “ Chicago P.D .” concluding the event at 10 p.m.