The Dead Man Walking star headed to the poverty-stricken country in December (11) with her actress daughter Eva Amurri to raise awareness about child trafficking and the work of the Somaly Mam Foundation, which aims to put a stop to the crime.
During her trip, Sarandon and Amurri visited a working brothel - and they were horrified to see the tot living with her prostitute mum in such sad circumstances.
Speaking to U.S. talk show host Anderson Cooper, she said, "That (seeing the baby) was the thing that broke me. I was OK touring the houses and stuff, but to see that five-day-old perfect little girl, and know what lay ahead for her, and the mother had gone back to work already..."
But Sarandon was able to draw a positive from her journey - the emotional trip strengthened her bond with her own daughter: "We had a lot of time on the flights to and from (Cambodia) and that was very interesting because we got to talk about everything... It was very moving."