He offered his services to Thomas Griffiths, the Vicar Apostolic of the London District, who ordained him priest at St. Edmund's, Ware, 19 September 1840.
From the first he showed a warm sympathy with the Oxford converts and formed a friendship with John Henry Newman and Frederick Oakeley before they had become Catholics.
Nicholas Patrick Wiseman showed his appreciation of his priestly zeal by making him provost of the newly appointed metropolitan chapter and his vicar-general in 1850.
In 1857, Whitty obtained leave to resign his position, and entered the noviceship of the Society of Jesus at Verona.
Whitty filled other important offices, and worked until the end, giving ecclesiastical retreats even in the last summer of his life.