In this paper, multivariate calibration methods of partial least squares (PLS) and principle component regression (PCR) were investigated in simultaneously determination of hydrazine (HZ) and acetylhydrazine (AHZ). The aforementioned methods are based on formation of the silver nanoparticles (AgNPs) from the reaction of HZ and AHZ with Ag+ ions as oxidizing agent in the presence of citrate ions as a stabilizing and catalyzing agent. The reaction was followed by analytical wavelength (420 nm) corresponding to the maximum extinction of was related to surface plasmon resonance (SPR) of AgNPs. These methods were based on the differences observed in the production rate of AgNPs. Differences in the kinetic behavior of the HZ and AHZ were exploited using PLS and PCR to resolve concentration of analytes in their mixture. The obtained results show that simultaneous determination of HZ and AHZ can be performed in the concentration linear ranges of 40.0-1000.0 and 200.0-1000.0 ng mL-1, respectively. The root mean squares errors of prediction (RMSEP) for applying PCR and PLS methods to 9 synthetic samples in these concentration ranges were 0.8307 and 1.9411 for HZ and 1.4407 and 0.9883 for AHZ, respectively. To assess selectivity of the methods, the effects of certain foreign ions upon the reaction rate were determined. Both methods (PLS and PCR) were validated using a set of synthetic sample mixtures and then they were applied for simultaneous determination of HZ and AHZ in different water samples.