Dendrograms are considered as the most important visualization technique of Hierarchical Clustering. We studied the stability of different dendrograms on the Tehran Stock Exchange and then stabilized the system of TSE indices using Principal Component Analysis (PCA). It seems that the comparison of dendrograms before and after PCA is a quantitative measure of system stability. ( 43% in our study of 21 different indices of TSE which are the representations of the economic sectors of Iranian financial systems. We measured the similarity of different dendrograms according to Baker’s Index and the Cophenetic Correlation Index. The results show that stabilized hierarchical clusterings have got better Baker’s Index and more reliable dendrogram. Therefore, It is highly recommended to investors, portfolio managers and risk hedgers to denoise and stabilize their clustering with efficient methods like PCA before financial decision making.