Parkinson's disease (PD) is a neurodegenerative disorder, which may affact lives of many people by lowering their life quality and expectancy. PD is an expensive to treat disorder and increasingly encountered as the number of elderly increases. The disease is believed to be caused by the death of movement-controlling motor neurons present in substantia nigra pars compacta part of the midbrain. PD is usually diagnosed with the emergence of the classical symptoms namely bradykinesia, rigidity, tremor and postural instability. Diagnosis of PD is mostly a challenging task even for an experienced physician because several other neurological diseases display similar symptoms such as multiple system atrophy and Lewy body dementia. Early diagnosis of PD is not possible, yet essential because PD is diagnosed after the symptoms appear and more than 70% of the motor neurons have been lost. Therefore, discovery of a biomarker or a biomarker array that can be used for early diagnosis of PD would be a great help for patients as well as for the physicians. Proteomics approaches are often used in biomarker discovery. Proteomics can be briefly described as the study of proteoms in cells or in biological fluids and investigates the changes in proteoms under various physiological conditions. Proteomics sometimes referred to be the postgenomic era covers a braod range of research field from description of proteins to the functions of proteins. In this article, we aimed at reviewing and emphasizing the importance of proteomic studies carried out to discover a biomarker or a biomarker array in order to diagnose PD. Although there is no validated biomarker or a biomarker array for diagnosis of PD, promising results have been obtained.