A son of John Ward, a noted Puritan minister, he was born in Haverhill, Suffolk, England. He studied law and graduated from Emmanuel College, Cambridge University in 1603. He practised as a barrister and travelled in continental Europe. In Heidelberg he met a German Protestant reformer, David Pareus, who persuaded him to enter the ministry. In 1618 he was a chaplain to a company of English merchants at Elbing, in Prussia. He returned to England and in 1628 he was appointed rector of Stondon Massey in Essex. He was soon recognised as one of the foremost Puritan ministers in Essex, and so in 1631 was reprimanded by the Bishop of London, William Laud. Although he escaped excommunication, in 1633 he was dismissed for his Puritan beliefs. (Ward's two brothers also suffered for their non-conformity.)
In 1634 Ward emigrated to Massachusetts and became a minister in Ipswich for two years. He then resigned because of ill-health. While still living in Ipswich, he wrote for the colony of Massachusetts The Body of Liberties, which was adopted by the General Court of the Massachusetts Bay Company in December 1641. This was the first code of laws established in New England. The Body of Liberties defined liberty in terms that were advanced in their day, establishing a code of fundamental principles based on Common Law, the Magna Carta and the Old Testament. However, Ward believed in theocracy rather than democracy. One of his epigrams was:
Ward thought that justice and the law were essential to the liberty of the individual. Some have said that The Body of Liberties began the American tradition of liberty, leading eventually to the United States Constitution.
In 1645 Ward began his second book, The Simple Cobbler of Aggawam in America. This was published in England in January, 1646-7, before Ward's return there, under the pseudonym of Theodore de la Guard. Three other editions, with important additions and changes, soon followed. The Simple Cobbler is a small book, which "in spite of its bitterness, and its lack of toleration" is "full of quaint originality, grim humor and power", according to the anthology Colonial Prose and Poetry: The Transplanting of Culture 1607-1650 (1903).
According to the anthology, the book is "probably the most interesting literary performance" in the first half of the seventeenth century in the English colonies that later became the United States. The book was later reprinted in 1713 and 1843 in Boston, Massachusetts.
He also wrote several religious-political pamphlets.