Introduction <p>Sarcopenia and dynapenia are muscle-related conditions commonly associated with ageing, malnutrition, and functional decline. Despite their clinical relevance, few studies have explored their prevalence in institutionalized older adults in Portugal. This study aimed to determine the prevalence of sarcopenia and dynapenia and to explore their associations with sex, nutritional status, and body composition.</p> Methods <p>A cross-sectional observational study was conducted between March and July 2023 in four long-term Continuous Care Units (UCCs) in Lisbon. Forty-two individuals aged ≥ 65 years were assessed. Sociodemographic, clinical, anthropometric, and nutritional variables were collected. Sarcopenia risk was evaluated using the SARC-F questionnaire, and muscle strength was assessed by handgrip dynamometry. Calf circumference was used as a proxy for muscle mass. Nutritional status was determined using the Mini Nutritional Assessment^®.</p> Results <p>The mean age was 78.5 ± 6.7 years, and 69% were female. Sarcopenia risk was identified in 83.3% of participants using SARC-F, while confirmed sarcopenia (according to EWGSOP2 criteria) was present in 26.2%. Dynapenia, defined by reduced handgrip strength, was highly prevalent (95.2%), especially among women. Both sarcopenia and dynapenia were significantly associated with female sex, low BMI, and malnutrition or nutritional risk (<i>p</i> &lt; 0.05). Calf circumference &lt; 31&#xa0;cm was observed in the majority of sarcopenic individuals, suggesting its utility as a screening measure.</p> Conclusion <p>Dynapenia was more prevalent than sarcopenia in this institutionalized population. Both conditions were strongly associated with poor nutritional status and female sex. These findings highlight the importance of incorporating simple, accessible tools for early identification of muscle weakness and nutritional risk in long-term care settings, to improve health outcomes and guide targeted interventions.</p>