Seawater intrusion in coastal aquifers is investigated under transient conditions and the results are compared to steady-state results. A three-dimensional variable density model is developed and applied on an unconfined aquifer of relatively small rectangular shape. Pumping optimization is initially performed under steady conditions for obtaining optimal pumping rates. Several drought scenarios with a 10% reduction on the annual recharge rate are examined indicating a quick nonlinear decrease of sustainable freshwater as a function of recharge. Next, a monthly based variable density model is developed by distributing the annual recharge into twelve stress periods. A reference scenario based on real rainfall measurements is investigated and the results are then compared to two additional scenarios with different monthly recharge distributions. All three transient scenarios indicate an advancement of seawater wedge compared to the steady-state results, which should be taken into consideration in coastal aquifer management plans.