Background Quality of life is poorer in Parkinson's disease than in other conditions and in the general population without Parkinson's disease. Malnutrition also results in poorer quality of life. This study aimed at determining the relationship between quality of life and nutritional status. Methods Community-dwelling people with Parkinson's disease >18 years old were recruited. The Patient-Generated Subjective Global Assessment (PG-SGA) assessed nutritional status. The Parkinson's Disease Questionnaire 39 (PDQ-39) measured quality of life. Phase I was cross-sectional. The malnourished in Phase I were eligible for a nutrition intervention phase, randomised into 2 groups: standard care (SC) with provision of nutrition education materials only and intervention (INT) with individualised dietetic advice and regular weekly follow-up. Data were collected at baseline, 6 weeks, and 12 weeks. Results Phase I consisted of 120 people who completed the PDQ-39. Phase II consisted of 9 in the SC group and 10 in the INT group. In Phase I, quality of life was poorer in the malnourished, particularly for mobility and activities of daily living domains. There was a significant correlation between PG-SGA and PDQ-39 scores (Phase I, rs?=?0.445, p?=?.000; Phase II, rs?=?.426, p?=?.002). In Phase II, no significant difference in the PDQ-39 total or sub-scores was observed between the INT and SC groups; however, there was significant improvement in the emotional well-being domain for the entire group, X2(2)?=?8.84, p?=?.012. Conclusions Malnourished people with Parkinson's disease had poorer quality of life than the well-nourished, and improvements in nutritional status resulted in quality of life improvements. Attention to nutritional status is an important component of quality of life and therefore the total care of people with Parkinson's disease.