In 2019, he used a pocket veto to block the California Senate from considering SB 50, which would have allowed for denser housing construction near public transit.

At the request of the Screen Actors Guild in 2010, Portantino proposed an anti-gatecrashing law that would make party crashing a misdemeanor with punishments being up to six months in jail, or a $1,000 fine, or both.

[6] In 2022, he authored a bill that would provide $1.65 billion in tax credits through 2030 ($330 million per year) for film production in California.

[9] After six years of legislative effort, Portantino’s Senate Bill 805 was signed into law in 2023, expanding service and treatment options for autism.

In 2024, Portantino's Senate Bill 357 was passed, removing language from the vehicle code that discriminates against conditions such as epilepsy, protecting the doctor-patient relationship and improving access to care.

In 2022, Senate Bill 1016 improved educational access for an estimated 300,000 California students with Fetal Alcohol Spectrum Disorder (FASD).

In response by the 2012 decision of the U.S. 9th Circuit Court of Appeals to overturn Proposition 8, Portantino stated “My brother fought this battle for three decades.

[23] During a 2022 meeting with the Armenian National Committee of America, Portantino expressed a desire to improve trade relations between California and Armenia.

[26][27] In May 2019, Portantino, as Senate appropriations committee chair, used a pocket veto to temporarily block SB 50, a bill that would enact reforms to address the California housing shortage by reducing local control (such as allowing more apartment construction near public transit and in suburbs), from leaving committee to enter the Senate for debate and voting.

[28] In 2021, Portantino killed a bill that would have put an end to minimum parking requirements for certain new housing construction near transit stations.