Pharmaceuticals and personal care products (PPCPs) in swimming pool water are hypothesized to originate from fill water and anthropogenic sources like urine, sweat, swimwear and body surfaces. However, research exploring PPCP origins in pools is lacking. This research investigates PPCP sources at 31 swimming pools. Pool water was analyzed for 24 representative PPCPs using advanced liquid chromatography-mass spectrometry techniques. Fill water was analyzed as a contamination source and to determine if swimmers introduce PPCPs to pools. Results show every PPCP in fill water was present in pools except one, suggesting fill water is a PPCP source at pools. The presence of the antidepressant fluoxetine in 26% of pools and 0% of fill water indicates swimmers introduce pharmaceuticals. The flame retardant (tris(2-carboxyethyl)phosphine (TCEP)) was present 48% more frequently in pool than fill water, suggesting TCEP is introduced by body surfaces or swimwear. Enforcing showering and bathroom breaks is recommended to reduce PPCP contamination from swimmers.