The source detection sensitivity of Gaia is reduced near sources. To characterise this contrast sensitivity is important for understanding the completeness of the Gaia data products, in particular when evaluating source confusion in lower resolution surveys such as photometric monitoring for transits. Here, we statistically evaluate the catalogue source density to determine the Gaia Data Release 2 source detection sensitivity as a function of angular separation and brightness ratio from a bright source. The contrast sensitivity from ∼0.4″ out to 12″ ranges in ΔG = 0–14 mag. We find the derived contrast sensitivity to be robust with respect to target brightness, colour, source density, and Gaia scan coverage.