The study aimed to investigate the concentration-dependent effect of different essential oils on Candida albicans biofilm growth on denture reliners and their effect on the hardness of soft denture reliners. Soft liner specimens (n = 160) were fabricated and seeded with C. albicans. The specimens were distributed into four groups: one control group (n = 40) and three experimental groups (n = 40), namely lemongrass essential oil (LGO), tea tree essential oil (TTO), and thyme essential oil (ThO). The specimens treated with essential oil for 1-5 minutes were subsequently analyzed by biofilm adhesion assay, MTT assay, and scanning electron microscopy. Shore A hardness of the soft denture reliners was recorded after immersion. Inhibition activity of the oils in the order LGO > ThO > TTO was observed with a minimum of 5 minutes of treatment. LGO reduced biofilm formation at a concentration as low as 0.03125%. There was a significant linear increase in mean hardness values in all groups from baseline to day 60 with a statistically lesser increase rate in the TTO group. Disinfection with LGO and ThO was effective to remove the biofilm of soft reliners at very low concentrations without altering the hardness. Hence, LGO and ThO can be used as effective denture cleansers.