The agglomerative hierarchical cluster analysis was employed to evaluate the tropic status of the mangrove water quality of Okoro River Estuary, Southeastern Nigeria. Cluster analysis using the ward method with squared Euclidean distance measure was performed, which indicated the distribution of parameters and depicted different hydrochemical facies. The results yielded a dendrogram with four statistically significant clusters of similar behavour with the biggest cluster of seven (7) parameters. The water parameters were classified into mutually exclusive unknown groups that share similar characteristics and properties. Dendrogram clearly distinguished parameter bahaviours and interprets the description of the hierarchical clustering in a graphical format. The dendrogram showed a moderate cophentic correlation coefficient (C= 0.72) among physicochemical parameters of mangrove water quality. The behavioural pattern of parameters and the agglomeration of nearest neighbour cluster indicated that the process of salinization, organic decomposition, mineralization, metal accumulation and surface runoff characterized the mangrove water quality of the area. The Euclidean distance revealed the extent of similarity and dissimilarity between water quality characteristics. The result of month-wise hierarchical cluster analysis showed discrimination of the months with similar environmental and physicochemical behaviour. This study illustrates the benefit of agglomerative hierarchical cluster analysis for the characterization, evaluation and interpretation of complex dynamism in the mangrove dominated area of southeastern Nigeria and recommends regular monitoring and assessment of mangrove water quality.