The conditions of social distancing and home confinement imposed to contain the outbreak of the severe acute respiratory syndrome coronavirus 2 (COVID-19) pandemic have changed the dietary patterns and lifestyle of society. These changes have had significant consequences not only for our personal well-being but also for the health of the planet. In this context, the aim of this study was to describe the effect of household containment during the COVID-19 pandemic on greenhouse gas (GHG) emissions related to food and water consumption. In addition, the dietary pattern of the Spanish population during home confinement was compared with the usual dietary pattern of consumption for the immediately preceding reference year (2019) to elucidate in depth the environmental consequences derived from food consumption due to COVID-19 restrictions. Life Cycle Assessment (LCA) and Water Footprint Assessment (WFA) methodologies were used to assess carbon footprint and water footprint. The functional unit of reference was the average daily food intake per capita. The results showed that COVID-19 home confinement had a negative impact on the carbon footprint (CF) and water footprint (WF) of the Spanish dietary pattern mainly due to the increase in the amount of food consumed during 2020. The monthly analysis revealed two peaks in April and October for both environmental indicators in 2020 compared to the same period in 2019, which was mainly due to the increase in food consumption in Spanish households during the weeks of confinement as well as to the new COVID-19 wave in October. On the other hand, an upward trend in GHG emissions and water consumption could be observed in the last months of both years, which is attributed to increased consumption during the Christmas holidays. These findings indicate that people should be more aware than ever of the importance of maintaining a healthy lifestyle and dietary pattern, in line with health guidelines and the Sustainable Development Goals.