The coronavirus (COVID-19) pandemic has led to isolation of people that need to remain at home to prevent infection. Lockdown measures were implemented making major changes and impact on the lifestyle, mental health, and quality of life of citizens, particularly among the elderly. The aim of this descriptive-correlational study was to investigate the impact of COVID-19 lockdown on lifestyle behavior, mental health, and quality of life of 100 elderly in Barangay Platero, City of Biñan, Laguna. The findings reveal that there is a significant change in diet, physical activity, and sleep of elderly during lockdown period; 91% indicated possible depression (GDS-5); 81% with mild anxiety (GAD-7). There is also an agreement among the respondents that the lockdown has an impact on the quality of their life. Moreover, the impact of COVID-19 lockdown on lifestyle behavior is associated with GDS and quality of life. However, GDS-5 and GAD-7 are not associated with quality of life which can be attributed to the fact that the elderly can still manage to have a better and normal life though they were worried and upset because of the strict quarantine measures.