Thirdhand smoke (THS) is the residue remaining after active tobacco smoking has occurred. The residue can mix with other pollutants in the air, creating new and harmful compounds that settle on indoor surfaces such as walls, carpet, and furniture. Once tobacco smoke pollutants adhere to surfaces, they become difficult to remove and remain in the environment. In the state of California, smoking is prohibited in restaurants, bars, and the workplace. California tribal casinos are one of the few public establishments that are exempt from enforcing bans on smoking. As a result, tobacco smoke exposure continues to pose a threat to casino employees and nonsmoking patrons. One casino located in Redding, California, voluntarily made the decision to implement a 100% smoke free policy. In this study, levels of surface nicotine, a marker of THS, was measured from smoking and nonsmoking areas of the casino before and after implementing the smoking ban. For sampled surfaces, 10 cm by 10 cm area was wiped with cotton rounds wetted with 0.1% ascorbic acid solution and transported frozen. Samples were spiked with deuterated nicotine and analyzed using liquid chromatography—tandem mass spectrometry (LC-MS/MS). Levels of surface nicotine were significantly higher in smoking vs nonsmoking areas of the casino well before and after the smoking ban (p<0.001). The median surface nicotine level in combined smoking areas (1-4) before smoking ban was 1615 _g/m_ and 247 _g/m_ up to 6 months after smoking ban. In nonsmoking areas the median surface nicotine level before smoking was 3.4 _g/m_ and 2.6 _g/m_ after smoking ban. Overall, levels of surface nicotine decreased over a 6 month period, but levels in the smoking area were not significantly different in the month following the ban than levels before the ban. This study demonstrates that THS persists even after active smoking has ceased and can expose patrons and employees to tobacco pollutants.