For the second year in a row, the month of May activities opened with the Grand Prix of Indianapolis over May 7–9. Practice opened on May 11, and time trials were held on May 16–17. Rain interrupted and eventually washed out time trials on May 16, and all qualifications were held on Sunday May 17.

The 2015 race saw the debut of unique aero kits from Chevrolet and Honda, respectively, outfitted for the Dallara DW12 chassis. As part of the ICONIC project, aero kits were originally planned for 2012, but a series of delays due to cost issues put off their homologation and implementation until 2015. During practice, three Chevrolet entries suffered major crashes that resulted in flip-overs. The crashes raised safety concerns around the paddock, and series officials delayed time trials for several hours in order to address the situation with rule and procedural changes, removing qualifying from its status as a points-paying event.

During a practice session on May 18, IndyCar's Holmatro Safety Team was lauded for a life-saving effort in their rescue of driver James Hinchcliffe. During the run, Hinchcliffe was involved in a major crash, and was impaled by a suspension member. The rapid response by the medical crews was credited with likely saving his life, and nine days later he was released from Methodist Hospital, expected to make a full recovery. Hinchcliffe was able to drive the IndyCar two-seater at a promotional event in August at the Golden Gate Bridge, then made his first competitive laps in a Dan Wheldon Memorial karting event in September.

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