Structured environments are employed in a plethora of applications to tailor dynamics of light–matter interaction processes by modifying the structure of electromagnetic fields. The promising example of such a system is antiresonant photonic crystal fibers (AR-PCFs), which allow light–analyte interactions in a very long channel. Here we probe contribution of microstructuring and nontrivial mode hierarchy on light–matter interactions in AR-PCFs by investigating lifetime shortening of perovskite (CsPbBr3) nanocrystals grown to fiber capillaries. The crystals have been deposited using a wet chemistry approach and then excited by a supercontinuum source in the 450–500 nm range. Emission spectra have been measured and analyzed via the time-correlated single photon counting (TCSPC) technique, unravelling contributions of core and cladding modes. Fluorescence lifetime imaging inside an AR-PCF enables mapping input of various electromagnetic channels into light–matter interaction processes. Our results pave the way for tailoring the dynamics of high-order quantum processes, promoting the concept of AR-PCF as a light-driven reactor.