Muscle strength is a relevant metric of aging. Greater adherence to Mediterranean diet is associated with better health outcomes across all life stages; however, evidence on the relationship between Mediterranean diet and muscle strength in older adults is inconclusive. In this study, we evaluated the relationship between adherence to Mediterranean diet and handgrip strength in a large sample of community-dwelling older adults from the Longevity Check-up 7+ project. A total of 2963 participants (mean age 72.8 ± 5.7 years; 54.4% women) were analyzed. Mediterranean diet adherence was evaluated using a modified Medi-Lite score and categorized as low (≤8), good (9 to 11), or high (≥12). Handgrip strength was categorized as normal or low according to cut-points by the European Working Group on Sarcopenia in Older People 2. Older adults with lower Mediterranean diet adherence had a significantly higher prevalence of probable sarcopenia (25.9%) than those with good (19.1%) or high (15.5%) adherence. The proportion of participants with probable sarcopenia increased with age, but it remained lower in the good and high adherence groups. Logistic regression showed that greater Mediterranean diet adherence was associated with a lower risk of probable sarcopenia. Older age, female sex, and physical inactivity were associated with a greater risk of probable sarcopenia. Our findings emphasize the positive association between healthy lifestyles, including adherence to Mediterranean diet, and physical function in old age.