The effects of internally stored water on long-term deformations of high-performance concrete (HPC) were examined on 130 creep and shrinkage specimens and 750 compressive strength specimens. Creep and shrinkage were monitored for 500 days on sealed and unsealed concrete specimens using either normalweight or lightweight aggregate with different initial moisture conditions. The use of prewetted lightweight aggregate decreased creep by approximately 45% when compared with mixtures with air-dried lightweight aggregate. HPC with prewetted lightweight aggregate experienced creep that was 10% lower than that obtained in a similar HPC with normalweight granite aggregate. It is proposed that the reduction in creep with the prewetted lightweight aggregate is due to hydration enhancement, expansion afforded by internal curing, and by inhibition of water seepage.