[2] Prior to his election to the State Senate in 2016, Wiener served on the San Francisco Board of Supervisors representing the 8th district.

[5][6] Wiener was born to a Jewish family[7] in Philadelphia, Pennsylvania, and grew up in southern New Jersey, the son of small business owners.

[25] His proposals included changing the transit-impact development fee[25] and a ballot measure to tie Muni funding to population growth.

[30] The legislation included creating a centralized Street Design Review Committee, making it easier for developers to implement pedestrian safety projects as gifts to the city, and amending the Fire Code to provide more leeway for sidewalk extensions.

In 2013, Wiener's legislation establishing guidelines for San Francisco's food truck industry was passed by the Board of Supervisors.

[38] On the Budget Committee, Wiener advocated for adding government funding for maintenance and safety in San Francisco's parks and other public spaces.

[46] In September 2014, in an online essay on the Huffington Post, Wiener revealed that he was taking Truvada, a pre-exposure prophylaxis (PrEP) that reduces the risk of HIV infection.

[48] He also worked with David Campos to support ensuring low-cost access to Truvada for pre-exposure prophylaxis against HIV after Wiener revealed his own PrEP use.

[54] In 2014, Wiener introduced a ballot measure that would have imposed a two cents per ounce tax on the distribution of sodas and other sweetened beverages, and used the money to fund "healthy choices" in San Francisco.

[56] The proposal was endorsed by much of San Francisco's local political establishment, including all its state legislators, and many health organizations,[57] but voters in the November 4, 2014, election did not give the measure the 2⁄3 supermajority required to impose a new tax.

[59] In 2021, Wiener authored, sponsored, and introduced SB-519, a bill that provides for the decriminalization of psilocybin, DMT (N,N-Dimethyltryptamine), LSD (lysergic acid diethylamide), ibogaine, ketamine, mescaline, and MDMA (3,4-methylenedioxymethamphetamine) in the state of California.

[61] It headed to the California Assembly for a vote to determine final approval, however, after a third reading it was ordered to the inactive file on August 25, 2022, by Assemblywoman Eloise Gómez Reyes.

[72] In October 2019, Governor Gavin Newsom signed Wiener's legislation expanding access to HIV-prevention medications PrEP and PEP.

[82] In 2021, Wiener authored SB 107, a "trans refuge bill" to protect transgender children seeking gender affirming care in California and their families from civil and criminal punishment under other states' laws.

[88] Senate Bill 700 created a 10-year program to give rebates to customers who install energy storage systems, including batteries.

[93] In 2019, Wiener co-authored Senate Bill 27, which would have required presidential candidates to disclose their tax returns to be eligible to appear on a California primary ballot.

The bill received a veto from Governor Newsom due to opposition from Caltrans over its cost and the potential loss of federal highway funds.

"SB 35 sets clear and reasonable standards to ensure that all communities are part of the solution by creating housing for our growing population.

[109] In 2018, in an effort to address the state's housing affordability crisis and CO2 emissions, Wiener introduced Senate Bill 827, which would require cities and counties to allow apartment buildings of four to eight stories in "transit rich areas"—defined as land within a half-mile of a major transit stop or a quarter mile of a stop on a high-frequency bus route.

In 2022, Wiener co-authored SB 886, which would exempt the UC, CSU and community college systems from the lengthy California Environmental Quality Act (CEQA) review process.

Wiener also co-sponsored AB 2097, which abolished parking minimums for homes and commercial buildings within a half-mile (0.80 km) of public transit, or for neighborhoods with low rates of car use.

[127] Citing the cultural and economic benefits of nightlife, Wiener proposed legislation to allow cities to extend alcohol sales in bars and restaurants to 4 am.

[130] Wiener reintroduced the bill the following year, this time limited to six cities whose mayors had supported the idea: San Francisco, Oakland, Los Angeles, Sacramento, West Hollywood, and Long Beach.

[132] Governor Jerry Brown vetoed the legislation September 28, 2018, citing California Highway Patrol concerns over drunk drivers.

[127] Proponents say that it would help venues still recovering from the pandemic stay in business, while opponents say that it would add to alcohol-related problems, including DUIs in cities adjacent to those allowing later last calls.

[136] In February 2024, Wiener proposed SB 1227, one of the broadest rollbacks of the California Environmental Quality Act (CEQA) to allow most projects in downtown San Francisco to bypass the law for the next decade.

[137] In January 2024, Wiener proposed SB 961 that would require every passenger vehicle, truck and bus manufactured or sold in California to have speed governors starting in 2027.

[148] [149] Through CLJC Wiener played an important role in securing $80 million from the state budget for various Jewish community priorities for 2024-2025 [150] as well as a similar amount in 2021.

[154] Wiener and other CLJC officials commended California State University Chancellor Mildred García for placing Sonoma State University President Mike Lee on leave after Lee announced support for an academic boycott of Israel in agreement with protesters and Students for Justice in Palestine,[155][156][157] which was seen as aligning with the Boycott, Divestment and Sanctions (BDS) movement, and which Wiener described as “horrific and wrong”.

[165] In June 2022, Wiener was the victim of a false bomb threat, reportedly due to his work on behalf of the LGBT community.