Alexandria is the second-largest city in Egypt and the country's largest seaport that serves about 70% of the Egyptian imports and exports, especially the western harbor, which is the main commercial port and contains the Egyptian military naval base. Although Alexandria harbor has significant effect on the Egyptian economical income, there is still a shortage in coastal oceanographic discipline, specifically in the sea-level study that plays an important and effective role in many applications especially in chart production and dredging operations. Sea level is one of the oceanographic parameters that always needed in hydrographic surveying for depth reduction and chart datum realization. An imaginary surface, such as the Lowest Astronomical Tide, is recently used as the vertical tidal datum or chart datum that depths are referred to in all nautical charts. Therefore, sea-level measurements and analysis are always crucial for establishing an accurate datum precisely connected to onshore geodetic vertical datum to achieve the basic needs for mariners and hydrographers. Continuous and precise updating of tidal and terrestrial vertical datums connection and relationship, is of importance to provide essential information to many users including those in; commercial shipping industry, marine construction, water boundaries delimitation, marine safety, coastal areas planning, Engineering, chart datum for nautical charts production, in addition to military operations and many others. The geodetic vertical datum network in Egypt has been set as the mean sea level in Alexandria. This datum was first derived based on sea-level observations for eight years from 1898 to 1906. This imaginary surface was (34 cm) referred to the zero of the graduated staff in Alexandria harbor, and it was called the Egyptian Survey Authority datum. In each annual edition of the Admiralty Tide Tables, it was stated that the chart datum in Alexandria, as a secondary port in Egypt, is (-0.34 m) from mean sea level and all the essential known tidal levels were calculated and referred to Gibraltar as the standard port for Alexandria harbor on Mediterranean Sea. However, limited research has been updating this issue since most of the earlier studies of sea level in Alexandria Harbor dealt with sea level based on statistical computations without referring sea level measurements to a specific geodetic vertical datum. For most of the scientific applications especially in sea-level studies, the International Terrestrial Reference Frame (ITRF) is preferred. ITRF-2014 is the most accurate realization of the international terrestrial reference system. Delft-3D hydrodynamic flow model was used to model hourly sea level time series (19 yrs.). Bathymetric data acquired from chart digitization that was produced from hydrographic surveying operations, together with Era-interim meteorological data (1996-2006) compiled with Ras El-Tin automatic weather station data (2006-2016), all were employed as model's initial conditions beside other physical parameters. Boundary conditions were acquired from Achieving, Validation and Interpretation of the Satellite Oceanographic service (AVISO) for a daily sea level data, compiled with tidal constituents (amplitudes and phase angles) obtained from harmonic analysis of offshore observed sea level data from S4 current meter buoy (depth sensor) and the major tidal constituents parameters in the area from Delft-3D Dashboard tidal data. Model results were validated by results obtained from several observed sea-level data analysis. The analyzed hourly observed sea level time series was accurately referred to the tide gauge zero level which was geo-referenced to the latest geodetic terrestrial reference frame, data was recorded inside the harbor during two time periods (09/11/2008-08/22/2010) and (04/30/2012-10/25/2013). Besides, a short-term sea-level data from S4 buoy offshore outside the harbor during the period (10/26/2008-12/31/2008). From harmonic analysis of both modeled and observed sea level datasets inside and outside the harbor in the two different intervals using Delft-3D tide suit. It was concluded that sea level is mainly derived by tidal power with a power percentage between 53% and 81% to the total sea-level power respectively. These percentages are a result of 13 significant tidal constituents, dominated by the principal diurnal and semi-diurnal lunar tidal constituents (M2-S2-K1-O1). Besides, the solar annual (Sa) along with solar semi-annual (Ssa) tidal constituents which were found to contribute significantly with amplitude percentage ranged between (14% to 23%) for Sa and (2% to 13%) for (Ssa) to the total tidal constituents amplitudes, which reflects the seasonality effect that is related to the annual meteorological variations and thus affects sea-level changes in the area. The amplitude root means square error between both molded and observed datasets equal (0.005 m) and (0.012 m) respectively, that will not affect the accuracy of the major tidal datums determined. The cross-correlation analysis between modeled and observed sea level datasets demonstrated a strong correlation between tidal signals and moderate correlation in residuals with correlation coefficients equal (0.72) and (0.62) respectively, that confirmed the capability of Delft-3D flow model to precisely simulate variabilities and trends of observed oceanic conditions reasonably in Alexandria Harbor. From form factor percentage of both modeled and observed datasets it was signified that the tidal type regime in Alexandria Harbor is semidiurnal with a (0.25) ratio. From analyzing long-term modeled sea-level dataset (19 yrs) during the period (01/01/1996 till 11/30/2015), a positive linear trend was resulted by a rate of 3.4 mm/yr that agrees with the global sea level rise rate. From tidal vertical datums calculations of both modeled and observed datasets, the ellipsoidal heights of lowest and highest astronomical tide datums considering ± 10 cm safety margin were updated and suggested to be (14.29 m) and (15.23 m) referred to the international terrestrial reference frame 2014 respectively, with a range equals (94 cm), while the suggested same datums ellipsoidal height values referred to the world geodetic system 1984 are (14.36 m) and (15.20 m) respectively, with a range equals (84 cm). Finally, the ellipsoidal height values of the most essential used vertical datums referred to both geodetic datums ITRF-2014 and the World Geodetic System 1984 (WGS-84) were re-visited and updated from both modeled and observed sea-level datasets for Alexandria Harbor.