To study the influence of curing conditions on the mechanical performance of concrete containing waste plastic aggregate several mixes were produced with replacement ratios of 0%, 7.5% and 15% of natural aggregates by three types of plastic aggregate. The mechanical performance was evaluated under three curing environments (laboratory conditions, wet chamber, and outer environment) to represent different conditions concrete may be subject to.Increasing the ratio of plastic incorporated and its size leads to a fall in compressive and splitting tensile strength and modulus of elasticity of concrete. It improved its wear resistance to abrasion, however.Damper environments were best for the performance of concrete without plastic. The sensitivity of concrete with plastic to curing conditions changes with the replacement ratio and depends on the property being studied. With higher percentages of plastic the mixed curing environments tended to give the best results for the properties most dependent on the bond between the plastic waste aggregates and the cement paste. It was also found that the response of concrete to the incorporation of plastic differs between curing regimes.