Background: In health care and in society at large, sarcopaenia is a disorder of major importance that can lead to disability and other negative health-related events. Our study aim is to determine the prevalence of sarcopaenia among older people attended in primary care and to analyse the factors associated with this age-related clinical condition; (2) Methods: A multicentre cross-sectional study was conducted of 333 community-dwelling Spanish adults aged 65 years or more. Sociodemographic, clinical, functional, anthropometric, and pharmacological data were collected. Sarcopaenia was defined following European Working Group on Sarcopaenia in Older People (EWGSOP) criteria; (3) Results: Sarcopaenia was present in 20.4% of the study sample, and to a severe degree in 6%. The intensity of the association between sarcopaenia and frailty was weak-moderate (Cramer V = 0.45). According to the multinomial logistic regression model performed, sarcopaenia was positively associated with age and with the presence of psychopathology (OR = 2.72; 95% CI = 1.30–5.70) and was inversely correlated with body mass index (OR = 0.73, 95% CI = 0.67–0.80; (4) Conclusions: Sarcopaenia commonly affects community-dwelling older persons and may be associated with age, body mass index, and psychopathology. The latter factor may be modifiable or treatable and is therefore a possible target for intervention.