Okmok volcano on Umnak Island, Alaska is one of the most hazardous, explosive volcanoes in the Aleutians. Most recently, it erupted in 2008. Previous seismic imaging of Okmok’s large caldera system revealed complex magmatic structures in the upper 5 km beneath the caldera but magma transport at larger depths remains poorly constrained due to reduced imaging resolution. Using receiver function analysis of waveforms, we aim to chart sharp boundaries in the crust beneath Okmok and the surrounding region in order to understand its deeper crustal magmatic system. We have calculated receiver functions for M6 and larger teleseismic earthquakes between 2008 and 2021 recorded by permanent networks AV and AK, and between 2015-2016 at temporary network 5F. We observe Ps arrivals that are consistent with a Moho depth of ~40km, particularly at stations outside the caldera. At some stations, we observe that receiver functions calculated for incoming rays pointing towards the volcano are different from those pointing away from the volcano. However, there is significant variability in the receiver functions, even for overlapping ray paths in the mid-to-deep crust (> 10 km). This suggests complex crustal structure with heterogeneity that may be spatially localized beneath individual stations. Furthermore, receiver functions for stations inside Okmok caldera are more reverberatory than those outside the caldera, indicating that the structure, likely predominantly in the upper crust, beneath these two regions is different.