Patrick A. Collins was born on March 12, 1844, in Fermoy, County Cork, Ireland. After the death of his father he and his family immigrated to the United States in 1848 and settled in Chelsea, Massachusetts. With limited formal education, he worked his way up in the upholstery trade, became involved in union activities and began to study the law. He graduated from Harvard Law School and was admitted to the bar in 1871. In 1873, he married Mary E. Carey, and they had three children, Paul, Marie, and Alice.
Collins also entered politics starting first as a Massachusetts State Representative in 1868 and then a State Senator in 1870. He served as a Democratic Congressman from Massachusetts from 1883-1889 and then was appointed Consul General to London by President Grover Cleveland from 1893-1897. He was also heavily involved in Irish politics, becoming president of the American Land League in 1880, a branch of the Land League (Ireland), an organization which fought to abolish landlordism in Ireland.
In 1901 Collins was elected mayor of Boston and served in that position until his death on September 14, 1905.