Lagos Cházaro studied for a legal career in Veracruz, Puebla and Mexico City.

In 1909, he joined the antireelectionist movement against President Porfirio Díaz led by Francisco I. Madero.

Lagos was personal secretary of General Roque González Garza when the latter was named president of the Republic by the conventionalists.

Lagos became president himself by authority of the Convention of Aguascalientes in succession to González Garza on June 10, 1915.

He lived in Costa Rica, Honduras and Nicaragua until returning to the country in 1920, after the end of the revolution.