Dillingham became Master following the departure of Anthony Tuckney to be Master of St. John’s, having been admitted to the College in 1636 and elected a Fellow in 1642.
He is said to have been more interested in his private studies and literary pursuits than in the government of the College: certainly the numbers and social status of the students continued to decline during his Mastership. He published biographies in Latin of Chaderton, the first Master of Emmanuel, and Archbishop Usher. In opinion he was a moderate Puritan.
In 1660 he contributed a loyal introduction to a collection of Latin poems published by the University to celebrate the Restoration. However, he was deprived of his position in 1662 and retired to Oundle, but remained on good terms with his successor Sancroft, corresponding with him, visiting the College and giving advice on the management of the estates.
In 1672 he married a widow with 7 children and became Rector of Odell, Bedfordshire, where he died in 1689.