α-Synuclein is found in plaques associated with Parkinson’s and other neurodegenerative diseases. Changes in α-synuclein oligomerization are thought to give rise to nucleation of neurodegenerative plaques. Here, we investigated the effect of hydrostatic pressure on the aggregation of α-synuclein in cultured neuronal cells. We found that hydrostatic pressure is associated with a transition from monomeric to higher order α-synuclein aggregates. We then tested whether this aggregation is associated with the loss of binding partners, such as phospholipase Cβ. We found that increased pressure reduces the level of PLCβ1 and the amount of α-synuclein/PLCβ1 complexes. These studies suggest that pressure promotes release of α-synuclein from protein partners promoting its oligomerization.