Alexander Sergeyevich Lebedev was born on September 20, 1884, in St. Petersburg to a family of a doctor. In 1902, he graduated from the Vvedenskaya Gymnasium, and in 1908, from the Military Medical Academy, earning the title of physician. After that, he was retained for improvement at the Department of Diagnosis and General Therapy. In 1911, he defended his doctoral dissertation and from 1912 worked as an assistant at the Department of Internal Diseases at the Petersburg Institute for Advanced Medical Studies under the guidance of Professor G. Yu. Yavein.

In 1918, Lebedev became a senior assistant at the Department of Diagnosis of Internal Diseases at the Medical Faculty of Saratov University, and in 1920, he headed the Department of Infectious Diseases at the same university.

On December 5, 1921, he was elected professor of the Department of Hospital Therapy at the Medical Faculty of Perm University. After moving to Perm, he organized a clinic for hospital therapy in 1922, which he directed until 1940.

From June 8, 1927, to 1928, Lebedev was a member of the university board, vice-rector, and head of the scientific and educational department.

After the establishment of the medical institute in 1930, he taught at the Department of Hospital Therapeutic Clinic and served as the director of the propaedeutic clinic of the institute.

From 1940 to 1945, Lebedev worked at the dental institute, heading the Department of Internal Diseases. From 1946 to 1952, he returned to the medical institute as a professor and head of the Department of Propaedeutics of Internal Diseases, continuing to collaborate with the dental institute until 1948.

In 1952, due to deteriorating health, Lebedev left his position at the institute but continued to work as the chief therapist of the city until 1953.

Lebedev was highly respected as a clinician and diagnostician, having established his own school. His students, such as N. N. Diakonov and A. V. Seleznev, became professors, and about 20 others held positions as associate professors and assistants.

Lebedev and his colleagues published more than 90 scientific works, and under his supervision, 8 candidate dissertations were defended. His scientific interests included blood diseases, hematopoiesis processes, pathologies of the digestive organs, and the clinic of rheumatism.

Lebedev was an outstanding administrator and an active public figure. In the 1927-1928 academic year, he was a member of the university board and headed the scientific and educational department.

In the 1930s, Lebedev created a stationary facility based on the therapeutic department of the Motovilikha Hospital for the rehabilitation of certain groups of patients, which became a prototype for modern sanatoriums and prophylactic institutions.

During the Great Patriotic War, he consulted the clinic of the V. M. Molotov plant No. 172 and evacuation hospitals No. 3148 and No. 1017.

In the post-war years, starting in 1949, Lebedev served as the chief therapist of the city and was a consultant in many hospitals and clinics, as well as evacuation hospitals.

He was elected a deputy of the Molotov City Council in 1934 and 1940 and was a member of the All-Union Society for the Dissemination of Political and Scientific Knowledge.