Eagan was elected as a Democrat to the Sixty-third and to the three succeeding Congresses (March 4, 1913 – March 3, 1921). He was a delegate to the 1920 Democratic National Convention at San Francisco, California. He was an unsuccessful candidate for reelection in 1920 to the Sixty-seventh Congress. He was again elected to the Sixty-eighth Congress (March 4, 1923 – March 3, 1925) but was an unsuccessful candidate for renomination in 1924.