Cerrón joined the Socialist Party in 2007. In 2008, he was one of the founders of the Free Peru party, where he was the national economic secretary.[2] After Free Peru member and congressman Álex Paredes González retired, Cerrón was elected as the spokesman of the party.[5]
After Pedro Castilloattempted to dissolve congress Waldemar Cerrón stayed quiet in the immediate aftermath, although he did vote to remove Castillo,[6] and later voiced support for Dina Boluarte.[7] In March 2023, Cerrón introduced a bill which proposed that preventive detention be limited to only 12 months, which was seen as some to be an attempt to free Castillo, who was in prison for 12 months.[8]
An investigation was opened in April 2021 into Waldemar Cerrón and his brothers Vladimir and Fritz's finances, specifically looking for evidence of money laundering.[11] Waldemar and Vladimir were found guilty, being sentenced to four years in prison. They stand accused of accepting money for an airport without government authorization. They escaped to an unknown location, with Interpol releasing a Blue notice.[12] Waldemar joked on social media that "they won't capture me in Peru".[13]