Weak gravitational lensing depends on the integrated mass along the line of sight . Baryons contribute to the mass distribution of galaxy clusters and the resulting mass estimates from lensing analysis . We use the cosmo-OWLS suite of hydrodynamic simulations to investigate the impact of baryonic processes on the bias and scatter of weak lensing mass estimates of clusters . These estimates are obtained by fitting NFW profiles to mock data using MCMC techniques . In particular , we examine the difference in estimates between dark matter-only runs and those including various prescriptions for baryonic physics . We find no significant difference in the mass bias when baryonic physics is included , though the overall mass estimates are suppressed when feedback from AGN is included . For lowest-mass systems for which a reliable mass can be obtained ( M _ { 200 } \approx 2 \times 10 ^ { 14 } M _ { \odot } ) , we find a bias of \approx - 10 per cent . The magnitude of the bias tends to decrease for higher mass clusters , consistent with no bias for the most massive clusters which have masses comparable to those found in the CLASH and HFF samples . For the lowest mass clusters , the mass bias is particularly sensitive to the fit radii and the limits placed on the concentration prior , rendering reliable mass estimates difficult . The scatter in mass estimates between the dark matter-only and the various baryonic runs is less than between different projections of individual clusters , highlighting the importance of triaxiality .