This study aims to explore the associations between nutritional status and health-related quality of life, physical activity, and sleep quality in older exclusively Caucasian adults from Greec who were free of any severe disease. This is a cross-sectional study. Mini Nutritional Assessment was used to assess nutritional status, health-related quality of life was assessed using the Short Form Healthy Survey questionnaire, sleep quality was assessed using the Pittsburgh Sleep Quality Index, and physical activity levels were assessed via the International Physical Activity Questionnaire3405 community-dwelling men and women, over 65 years old from14 different Greek regions were enrolled. Ten-point four percent (10.4%) of the participants were classified as malnourished, while 35.6% were “at risk of malnutrition”. A better nutritional status was significantly and independently associated with higher physical activity levels (p = 0.0011) and better quality of life (p = 0.0135), as well as better sleep quality (p = 0.0202). In conclusion, our study highlights the interrelationships between a good nutritional status, a high-quality sleep, active lifestyle, and good quality of life. Further interventional studies are needed to clarify the associations, and test the feasibility of improving the nutritional status, physical activity levels and sleep quality of the elderly, and the impact of these changes on quality of life, and healthy ageing in races beyond Caucasian populations. Public health strategies and policies should be recommended to inform older adults for the necessity to improve their nutritional status and lifestyle habits to improve their health status and to obtain better life expectancy.