There are 26 15-letter words that start with 'trans'.
Note: These 26 15-letter words that start with 'trans' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with transf, transp, transm, transi, transl, transc, transv, transa, transs, transg, transd, transu, transe, transh, transo, transn, transt.
7-letter words start with 'trans' (2)