Miller attended New York University, where he received his Bachelor of Arts degree in 1888. After attending Columbia University, he earned his Law Degree in 1891. He played lacrosse at New York University and also captained the team when he was an undergraduate there. Cy continued to play the game with the Staten Island Athletic Club Lacrosse team, which he captained to the 1890 championship.
From 1895 to 1912, Cy played for the Crescent Athletic Club. Miller held the office of president of the Professional Lacrosse Association. He also was a member of the original Real Estate Board dealing with the extension of the New York Subway System, and a founder of the New York Real Securities Exchange. In 1917 he was appointed a member of the New York State and United States Food Administration Board.
Cy was the president of the Boro of Bronx, New York City from 1910 to 1914, as well as being a trustee of New York University. Cy served as an active member of the Executive Committee of the United States Intercollegiate Lacrosse Association for many years. Cy Miller passed away in 1956.