A 100X broad-spectrum phosphatase inhibitor cocktail containing four phosphatase inhibitors. In this cocktail, sodium fluoride inhibits serine/thronine phosphatases and acid phosphatases, sodium orthovanadate inhibits protein tyrosine phosphatases and alkaline phosphatases, sodium pyrophosphate inhibits PP1 and PP2A, and beta glycerophosphate inhibits serine and threonine phosphatases. This cocktail can be added to lysis buffers, and can be combined with necessary protease inhibitors.