Trigger information is an important part of the ATLAS event data. In the EventIndex trigger information is collected for various use cases, including event selection and overlap counting. Decoding trigger information from the event records, stored as a bit mask, requires additional input from the condition database and the Monte Carlo trigger database, as trigger configurations evolve with time. Trigger information decoding depends on the run number for the recorded data and from the settings for Monte Carlo simulation. This article describes trigger information handling in the EventIndex and the interfaces used to access it.