[7] Mattiello has also expressed the fact that he does not support the bill relating to the Pawtucket Red Sox that was passed in the Senate in January 2018 and states that it was dead.

He has expressed his disinterest in the idea of the taxpayer's money funding the new stadium, leading to the team to look outside of Rhode Island.

[6][9] In 2018, Mattiello sponsored legislation commonly known as "Kristen's Law" that allows life sentencing for anyone who sells, delivers or distributes an illegal drug that leads to a fatal overdose.

[11] In June 2019, Mattiello attempted to include $1 million in the R.I. budget to be allocated to a single chiropractor, Victor Pedro, despite R.I.'s Medicaid Medical Care Advisory Committee stating that "there wasn’t evidence that the treatment worked.

"[15] Rhode Island ships were the center of the Transatlantic Slave Trade, importing more enslaved Africans than any other North American British colony.