OBJECTIVE To characterize adult and older adult vaccination practices of physicians from various medical specialties in Brazil, identify the barriers influencing prescription of vaccines to these populations, and evaluate the physicians knowledge on routinely prescribed vaccines. METHODS Cross-sectional survey conducted in Brazil between June-August 2018. Eligible physicians included those from general practice/family medicine, geriatrics, cardiology, gynecology, endocrinology, infectious disease and pulmonology. The surveys questions addressed the physicians prescription habits, sociodemographic and clinical practice characteristics, barriers to vaccines prescription to adult and older adult patients, and physicians knowledge regarding routinely prescribed vaccines. The study focused on the vaccines recommended by the Brazilian Society of Immunization (SBIm) for adults and older adults. Study sample was stratified according to the number of physicians per specialty and Brazilian region. RESULTS A total of 1068 surveys were completed. The vaccines prescribed by the highest proportions of physicians were Influenza (>90% of physicians for adults and older adults), Hepatitis B (adults: 87%; older adults: 59%) and Yellow Fever (adults: 77.7%; older adults: 58.5%). Underprescription was reported by less than 20% of prescribing physicians for all adult and older adult recommended vaccines. The most common barriers to vaccination were the high vaccine cost, lack of time during appointments and lack of patient interest. Knowledge on target populations, dosage schedule and availability in the Unified Public Health System (SUS) was generally low. CONCLUSIONS The results showed a considerable variability of prescribing habits across recommended vaccines and medical specialties. Although most prescribing physicians seem to be aware of the importance of adult and older adults vaccination, knowledge deficits on vaccines target populations, dosage schedule and availability in the SUS may hamper their ability to prescribe vaccines to all patients with an indication.