Labor leader

After the war, he advocated for trade unionism^[1] and became one of the founding fathers of the labor movement in the Philippines.^[5] Promoting core labor standards, he called for the observance of^[2] workers' rights and welfare^[6] including the right to organize, to bargain collectively, and to strike. He also called for the ban on the use of child labor.^[2] As a labor leader, he led the push for restructuring the Philippine economy to create new job opportunities and protect workers from the rise of contractualization.^[5]

ALU

He was the founder of the Associated Labor Union (ALU) in 1954, becoming its president for a long time,^[1] by leading workers in Cebu ports.^[3] ALU would become the biggest labor union in the country.^[5] Its major victory was the collective bargaining agreement brokered between the Visayan Cebu Terminal Co. and its workers in 1957, of which the workers began a strike a year earlier.^[2]

TUCP

In addition, he was also the founder of the Trade Union Congress of the Philippines (TUCP)^[7][8] that was established in 1975^[2] and led Visayas-Mindanao Conference of Trade Unions.^[1] He was TUCP president for 38 years until his retirement in 2011.^[7]

ASEAN Trade Union Council

He worked for the improvement of labor conditions both domestically and internationally.^[5] He was known as the secretary general of the ASEAN Trade Union Council.^[1] He was its founder in 1983, creating the organization with the objective of forwarding the rights of association workers.^[5] Together with other Filipino labor leaders, he called for the industrialized and oil-rich nations to a "rational approach" amidst the escalating oil price hikes.^[2]

International forums

From 1975 to 1996, he was a member of the governing body of the International Labour Organization (ILO) in Geneva.^[1] He represented the country and the Filipino workers as board member of the International Cofederation of Trade Unions (presently the ITUC) in 1975 until 1983, as well as the ILO International Centre for Advanced Technical and Vocational Training in Turin, Italy from 1968 to 1996. Also, he was the country's or the workers' group's delegate to the ILO annual conferences that occurred between the 1961 and 2005.^[9]

Social Security Commission

From 1968 to 1986, he was a representative on behalf of labor issues on the Social Security Commission,^[1] as well as labor adviser during the term of then President Corazon Aquino.^[10] He pioneered the establishment of labor centers in Quezon City, Cebu, Cagayan de Oro, and Davao City.^[11]

OPASCOR

Mendoza was key in transforming the National Arrastre and Stevedoring Corporation into a workers' enterprise called the Oriental Port and Allied Services Corporation (OPASCOR).^[12] It was also the result of Corazon Aquino's decision to privatize government corporations.^[13] The operator at the Cebu International Port responsible for overseeing shipments^[14] and granted with a 10-year contract by the Philippine Ports Authority on January 9, 1990, to exclusively service foreign vessels,^[13] it is the only company in the country that is owned 100 percent by its workers.^[14]

In 2002, then Senator John Osmeña initiated a legislative inquiry into the alleged diversion of company's funds into Mendoza's family-owned businesses.^[13] The company sought the suspension of the investigation and filed a suit at the Supreme Court stating that the Senate had exceeded its jurisdiction and was committing grave abuse of authority.^[14]