Charvis will play at blindside flanker, with Llanelli's Dafydd Jones moving to No 8 at the expense of Bath's Gavin Thomas.
Humphreys replaces Bridgend's Gareth Williams, while another front-row alteration sees Pontypridd prop Gethin Jenkins preferred to Swansea tighthead Ben Evans.
Evans is dropped from the match-day squad of 22, with Llanelli's Martyn Madden named on the bench.
In the second row, Gareth Llewellyn is set to win his 74th cap when he makes his first start of the current Six Nations campaign in place of Steve Williams.
In the backs, Kevin Morgan is ruled out with a serious knee injury which means that Rhys Williams moves from right-wing to full-back and Mark Jones is recalled after missing Wales' defeats against England and Scotland.
Wales. R Williams (Cardiff); M Jones (Llanelli), M Taylor (Swansea), T Shanklin (Saracens), G Thomas (Bridgend), S Jones (Llanelli), G Cooper (Bath); I Thomas (Llanelli), J Humphreys capt (Bath), G Jenkins (Pontypridd); R Sidoli (Pontypridd), G Llewellyn (Neath); C Charvis (Swansea), M Williams (Cardiff), D Jones (Llanelli).