On 20 April 2010, the Deepwater Horizon oil drilling rig located 66 km southeast of the Louisiana coast exploded and, by the time the pipeline was capped in July, estimates of 4.9 million barrels of oil were released in the northern Gulf of Mexico. Polycyclic aromatic hydrocarbons make up a small percentage of petroleum (< 5%), but are the most toxic with known negative impacts on wildlife and humans. Because of their lifestyle and trophic standing, seabirds are often impacted by marine spills. To test for the presence of polycyclic aromatic hydrocarbons, we captured and tested blood in Common Loons (Gavia immer), a winter migrant that spends 4–5 months in the Gulf of Mexico. Common Loons were captured at night, using spotlighting and a large dip net off the Louisiana coast, during January–March in 2011 and 2012. A total of 38 Common Loons were caught and sampled (17 in 2011 and 21 in 2012). Both the concentrations and frequency of polycyclic aromatic hydrocarbons present in Common Loons appear to be increasing between years; however, concentrations were low (< 10 ppb). In 2012, petrogenic alkyl polycyclic aromatic hydrocarbons, those derived from petroleum, were significantly higher than pyrogenic polycyclic aromatic hydrocarbons, derived from combustion and anthropogenic sources. It remains unknown if current levels have any adverse impacts on Common Loon health, reproduction and survival.