Trichoderma harzianum is a soil-borne filamentous fungus that exhibits biological control properties. T. harzianum can prevent the growth of pathogenic fungi on many types of plant crops, providing a chemically benign alternative to fungicidal agents currently on the market. A proteomic approach was taken to separate and identify proteins from a strain of T. harzianum with well established biocontrol properties. We developed a method of extracting proteins under acidic conditions that increased the solubilisation of alkaline proteins and eliminated acidic cell wall artefacts from micro-organisms in general. Combined with the use of protease inhibitors, this sample preparation method resulted in hundreds of proteins from T. harzianum being extracted and separated by two-dimensional gel electrophoresis. Proteins were identified by a combination of matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry and liquid chromatography mass spectrometry (LC MS/MS). Manual de novo sequencing was conducted to obtain sequence tags on unidentified proteins. A total of 25 protein spots were positively identified from a whole-cell protein reference map of T. harzianum.