Armine was created a baronet on 28 November 1619 and succeeded to the estates of his father on 22 January 1622. He was elected Member of Parliament for Boston at least in 1624 and possibly in 1621 to replace Sir Thomas Cheek who sat for another seat. In 1625, he was elected MP for Grantham and in 1626 MP for Lincolnshire. He acted as assistant to the managers of the parliamentary impeachment of the Duke of Buckingham in 1626. In 1627, he refused to collect an arbitrary "loan" which the King had attempted to impose on Lincolnshire, and was imprisoned as a result. He was elected MP for Lincolnshire again in 1628 and sat until 1629 when King Charles decided to rule without parliament for eleven years. He was Sheriff of Lincolnshire in 1630 and Sheriff of Huntingdonshire in 1639.