in 2016. Pangilinan won a third term in the Senate in the
2016 elections, placing eighth overall with 15,955,949 votes. He ran under the
Koalisyon ng Daang Matuwid of
presidential candidate Mar Roxas. In October 2016, he was appointed interim president of the
Liberal Party, succeeding former
Transportation and Communications Secretary Joseph Emilio Abaya. His appointment was made permanent in August 2017. Originally part of the Senate majority of the
17th Congress, Pangilinan joined the minority bloc on February 27, 2017, alongside Senators
Bam Aquino,
Leila de Lima,
Franklin Drilon,
Risa Hontiveros, and
Antonio Trillanes. Pangilinan was among the co-authors of the
Universal Access to Quality Tertiary Education Act (
Republic Act No. 10931), which made tuition and other mandatory fees free for students in
state universities, colleges, and
technical-vocational institutions. This landmark law, championed primarily by Senator
Bam Aquino, was co-sponsored by Pangilinan along with many of his colleagues across party lines. After initial concerns about its budgetary impact were overcome, President
Rodrigo Duterte signed RA No. 10931 into law in August 2017. Pangilinan, along with other sponsors, emphasized that the law was in line with the
constitutional mandate to make
education accessible to all. According to Pangilinan, the law aims to modernize infrastructure and bridge the
digital divide, especially for students and rural communities. He authored the
Sagip Saka Act (; RA No. 11321) in 2019, a law aimed at improving farmers' incomes and modernizing agriculture. The
Sagip Saka Act institutionalizes direct purchase programs by government agencies and local government units from accredited
agricultural and
fishery cooperatives, thus bypassing
middlemen and the traditional bidding process. In February 2019, he abstained during the passage of the Rice Tariffication Law (RA No. 11203) due to concerns about its impact on farmers and later defended that decision. He stated he "had reservations precisely in supporting the measure", subsequently filing amendments to ensure
tariff revenues funded direct cash assistance to
rice farmers. Pangilinan welcomed proposals from the
Department of Agriculture to increase rice import tariffs and urged that tariff collections must reach and directly benefit farmers, warning that the law had not delivered intended support. As part of his social legislation advocacy in the Senate, Pangilinan co-authored the Student Fare Discount Act of 2019 (RA No. 11314). This law institutionalized a 20% fare
discount for students on all forms of
public transportation throughout the year. The measure guaranteed the existing student fare privilege by law and extended it to include weekends and semester breaks. Pangilinan, along with the bill's principal sponsors, Senators
Sonny Angara and
Bam Aquino, pushed for the passage of this relief for students amid rising transportation costs. Pangilinan also co-authored the Expanded Maternity Leave Act, which became law in 2019 (RA No. 11210). This law significantly increased the
paid maternity leave for working women in the Philippines from the previous 60 days to 105 days for those with normal deliveries (and from 78 days to 105 days for
cesarean deliveries). In May 2019, following the failure of the
Otso Diretso slate—of which he was
campaign manager—to win any seats in the
2019 senatorial election, Pangilinan announced his resignation as party president. However, his resignation was rejected by party chairperson and Vice President
Leni Robredo. In July 2019, following the start of the
18th Congress, Pangilinan filed Senate Bill No. 264 to define and ban
political dynasties in public office. As chair of the
Senate Committee on Constitutional Amendments and Revision of Codes during the 17th Congress, he used his platform to push for this long-stalled reform. Pangilinan publicly challenged President
Rodrigo Duterte in 2020 to certify the anti-dynasty bill as urgent, arguing that such a law is necessary to dismantle oligarchic political structures and ensure equal opportunity in governance. However, like previous attempts by other legislators, Pangilinan's anti-dynasty initiative made little progress in Congress and "hardly moved" in committee deliberations. Pangilinan had been working on the coco levy issue in the Senate for years—he sponsored a coco levy
trust fund bill in the previous Congress that sought to implement a 2012
Supreme Court decision returning the levy to farmers. During debates on the 2021 measure, Pangilinan consistently pushed for provisions to ensure that
smallholder farmers would benefit. He argued that "farmer representation is the heart of the coco levy trust fund measure", insisting that coconut farmers themselves should have a strong voice in the fund's management committee. He also advocated defining a "small coconut farmer" as one owning not more than five hectares of land, to focus the law's benefits on poor and marginal farmers. Pangilinan worked with colleagues to revise the bill, and the refined measure was eventually enacted in February 2021. During the
COVID-19 pandemic-related
community quarantines, Pangilinan urged the government to shoulder the cost of
COVID-19 testing kits for inbound travelers, particularly
overseas Filipino workers. In 2021, Pangilinan co-authored the COVID-19 Vaccination Program Act (RA No. 11525), which aimed to expedite the procurement and distribution of
vaccines nationwide. == 2022 vice presidential campaign ==