There are 14 words that start with 'mutt'.
| mutt | mutts | mutter | 
| mutton | mutters | muttons | 
| muttony | muttered | mutterer | 
| mutterers | muttering | muttonfish | 
| muttonchops | muttonfishes | |
Note: These 14 words that start with 'mutt' are found from the USA & Canada version of the tournament Scrabble word list.