Sea level as a major oceanographic parameter is always needed in the field of hydrographic surveying for Chart Datum (CD) realization. Lowest Astronomical Tide (LAT) is a physical surface and the most recent used tidal datum as defined by the International Hydrographic Organization (IHO); "The lowest tidal level may occur under average meteorological conditions and under combination of any astronomical conditions" (IHO, 2011). It was adopted to be used as the vertical tidal datum for depths reduction on nautical charts. In the current paper, the main objective is to calculate the height of (LAT) referred to the mean sea level in Al-Ahmadi harbor, Kuwait. Sea level data were measured by sea level sensors using offshore Acoustic Doppler Current Profiler (ADCP). Simulated sea level time series was acquired from Delft-3D hydrodynamic model, and then it was used for chart datum calculation. Both observed and modeled sea level series were analyzed using harmonic analysis technique, to separate tidal from non-tidal components. Results of both data sets modeled and observed (tidal and non-tidal signals) were cross-correlated for model validation. Results showed a strong direct correlation between both tidal and residual components from both data sets by 97.93 % and 98.06 % respectively. Furthermore, from harmonic analysis it was found that M2 (Principal lunar semi diurnal), K1 (principal luni-solar diurnal), O1 (principal lunar diurnal) and S2 (Principal solar semi diurnal) are the most significant and dominant tidal constituents in the area. Moreover, tidal type regime Form Factor (FF) ratio shows a mixed semi-diurnal tidal regime by (0.85). These outcomes agree with the results obtained by (Pous, 2012; and Akbari, 2016) using shallow water model and 3D coastal ocean model respectively, for the same area. The tide asymmetry ratio, which is regarded as the major representation of harbor sediment transport, was 0.0193 and 0.0191, respectively, for both observed and modeled datasets, indicating that there is a distortion in tide wave in the area, with ebbdominant outflow sediment transport away from the harbor. Finally, from modeled sea level dataset, LAT as Chart-datum in the area was found (1.57 m) below Mean Sea Level (MSL), which is higher than the one calculated by the European Petroleum Survey Group (EPSG 5188) during mina Al-Ahmadi refinery construction in 2004 by (5 cm).