Objective: The objective of the study was to develop a simple, validated, and affordable visible spectrophotometric method for determination of piperacillin (PIP) present in bulk and powder for injection formulation. Methods: In the present method, cobalt thiocyanate (CTC) was used as a chromogenic reagent where it forms 2:1 ion pair complex at pH 2 with PIP which is having secondary and tertiary amine groups. Results: The formed bluish-green colored ion pair between PIP and CTC is quantitatively extractable into nitrobenzene with an absorption maximum of 665 nm. Regression analysis (r=0.9996) shows that the plotted calibration curve exhibits good linearity in the studied range of concentration (3–18 μg/mL). Low values of relative standard deviation (<2%) were observed indicating that the proposed method is reproducible, accurate, and precise. Conclusions: As per the existing guidelines of ICH (international council for harmonization of technical requirements for pharmaceuticals for human use), various parameters of the proposed method were tested for validation and can be used method of choice for routine analysis in industrial quality control laboratories, especially in developing countries.