The ex-Busted popstar tied the knot with Griffiths at a civil ceremony held at Rushton Hall, Northants, just weeks after he returned to rehab for the third time.
Celebrity guests at the wedding included Holly Willoughby, Myleene Klass and Willis's former bandmate James Bourne.
David Gest, a contestant with Willis on I'm A Celebrity..., was best man.
A guest told The Mirror: "Despite Matt's recent stint in rehab, there was booze at the wedding. But he had vowed not to touch a drop."