He is regarded as one of the founders of modern psychosurgery,[1] having developed the surgical procedure leucotomy—​better known today as lobotomy—​for which he became the first Portuguese national to receive a Nobel Prize in 1949 (shared with Walter Rudolf Hess).

He attended Escola do Padre José Ramos and the Jesuit-run College of Saint Fidelis and studied medicine at the University of Coimbra, graduating in 1899.

While serving as Dean of the Medical School at the University of Lisbon, he was arrested a third time for preventing police from settling a student-run protest.

During World War I, he was appointed the Ambassador to Spain, and afterward, he became Minister for Foreign Affairs in 1917, and in 1918 led the Portuguese delegation to the Paris Peace Conference.

[5] After a set of trials in rabbits, dogs, and cadaver heads,[8] he achieved success using 25% sodium iodide solution on three patients, developing the first cerebral angiogram.

He enlisted his long-time staff member and neurosurgeon Pedro Almeida Lima to test the procedure on a group of 20 patients, mainly with schizophrenia, anxiety, and depression.

[4] Instructed by Moniz, Lima performed ten of the first twenty surgeries by injecting absolute alcohol to destroy the frontal lobe.

[10] Moniz judged the results acceptable in the first 40 or so patients he treated, claiming, "Prefrontal leukotomy is a simple operation, always safe, which may prove to be an effective surgical treatment in certain cases of mental disorder.

After his initial procedures, other physicians, such as Walter Jackson Freeman II and James W. Watts, adopted a modified technique in the United States and renamed it "lobotomy.

His other writings included biographies of Portuguese physician Pedro Hispano Portucalense and José Custódio de Faria, a monk and hypnotist.

[15] Moniz's legacy suffered towards the end of the 20th century,[10] as leucotomies were then perceived overwhelmingly negatively, thought of as an outdated experimental procedure.

[16] Well-known experts, including Psychologist Elliot Valenstein,[17] and Neurologist Oliver Sacks, were particularly critical of Moniz's methods and him earning the Nobel Prize.