OBJECTIVES: This study evaluated the literature regarding the impact of adjuvant antiparkinson medications on disability and quality of life in patients with Parkinson’s disease. METHODS: Medline (Ovid) and PubMed (NLM) searches were conducted from 1996 to 2015, aided by an experienced librarian.   Eligible studies were randomized, placebo or active comparator-controlled clinical trials on patients with Parkinson’s disease, using at least one of the adjuvant antiparkinson medications including dopamine agonists, catechol-O-methyl transferase inhibitors (COMTIs), and monoamine oxidase type B inhibitors (MAOBIs)  and those reporting  patient reported outcomes  like  Parkinson's Disease Rating Scale (UPDRS) and 39-item Parkinson's Disease Questionnaire (PDQ-39). RESULTS: Overall, 403 titles and abstracts were screened and 390 citations were excluded. Data were extracted using a structured form. Two authors reviewed 13 full text articles independently and reached agreement to include 9 studies in the systematic review. The majority of clinical trials included in this review reported improvement of PDQ-39 and UPDRS ADL measures in patients treated with COMTIs or dopamine agonists; however, no studies on MAOB inhibitors met the eligibility criteria. One clinical trial did not find a significant improvement with UPDRS and one study did not find a beneficial effect on quality of life (PDQ-39) associated with the use of adjuvant antiparkinson drugs. Results from one study indicated that patients may benefit more, if COMTIs are started immediately after development of motor complications related to levodopa. CONCLUSIONS: The systematic review suggests beneficial effect of COMTIs and dopamine agonists than placebo on disability and quality of life of patients with Parkinson’s disease. More head-to-head comparative research involving adjuvant antiparkinson medications is needed to understand the treatment benefits.