In 2007, Weeraratna worked in the Laboratory of Immunology at the National Institute on Aging.[6] Weeraratna joined the Wistar Institute in 2011, first as an assistant professor and then as an associate professor and program leader of the Tumor Microenvironment and Metastasis Program at Wistar Institute.[2] In 2014, she was the recipient of an R01 grant from the National Cancer Institute.[7] In 2015, her research encompassed the effects of aging on skin and the corresponding changes in tumor growth.[8] She was named the Ira Brind associate professor, in 2016.[9] In receiving the professorship, Wistar Institute president and CEO, Dario Altieri remarked that "Dr. Weeraratna has demonstrated outstanding scientific initiative and is a great ambassador for our Institute...she is changing the way we understand melanoma, as she and her team seek ways to prevent and treat this dangerous disease.