The kinetics of biodegradation of single phenol and sodium salicylate (SA) and their binary mixtures in water by suspended Pseudomonas putida CCRC 14365 was studied at 30 °C and pH 7.0. Experiments were performed at different total substrate concentrations (0–4.25 mM) and/or mole fractions of phenol. The initial cell concentration was fixed at 0.025 g/L. Based on the parameters of the Haldane model for specific growth rate of the cells on single phenol and SA (correlation coefficient R2 > 0.9737), phenol had larger degradation rate than SA, whereas the inhibition of P. putida by phenol was less significant than by SA. That is, the cells were more favored to degrade phenol than SA under comparable conditions. On the other hand, the specific growth rate of the cells on binary substrates could be described by an extended Haldane equation (R2 = 0.9256). The substrate interactions were thus discussed according to the modeled parameters. The dynamics in the biodegradation of single and binary substrate systems was finally analyzed.