This lens will work on any Canon APS-C DSLRs including the EOS T3. This is an EF-S lens deisgned to work only on APS-C DSLRs, it will not work on full frame DSLRs. Don't even try it on a full frame DSLR, the lens element on the bottom sticks out a lot and will damage the mirror on the camera.
Yes this lens works great on a T3i I have the T2i and get incredible resaults on all of the T?I cameras it will work I believe anything EOS for that matter the EF-S lenses are designed to work on all crop sensor cameras are they an "L" series by no means No they are not as optically perfect, they are not starting at $ 900-$27000 I know the 3 i have blow the ef series out of the water on crop sensors an EF on a ful frame is incredible I own a prime 50 mm EF lens 90 mm on a crop sensor its to tight close up and not wide enough for big pictures artistically its perfect I am used to zoom lenses really wide or super tight. The EF-S lenses are awesome in my book.