Diacetyl, a suspected cause of respiratory disorders in some food and flavorings manufacturing workers, is also a natural component of roasted coffee. We characterized diacetyl exposures that would plausibly occur in a small coffee shop during the preparation and consumption of unflavored coffee. Personal (long- and short-term) and area (long-term) samples were collected while a barista ground whole coffee beans, and brewed and poured coffee into cups. Simultaneously, long-term personal samples were collected as two participants, the customers, drank one cup of coffee each per h. Air sampling and analyses were conducted in accordance with OSHA Method 1012. Diacetyl was detected in all long-term samples. The long-term concentrations for the barista and area samples were similar, and ranged from 0.013⿿0.016 ppm; long-term concentrations for the customers were slightly lower and ranged from 0.010⿿0.014 ppm. Short-term concentrations ranged from below the limit of detection (<0.0047 ppm)⿿0.016 ppm. Mean estimated 8 h time-weighted average (8 h TWA) exposures for the barista ranged from 0.007⿿0.013 ppm; these values exceed recommended 8 h TWA occupational exposure limits (OELs) for diacetyl and are comparable to long-term personal measurements collected in various food and beverage production facilities. The concentrations measured based on area sampling were comparable to those measured in the breathing zone of the barista, thus exceedances of the recommended OELs may also occur for coffee shop workers who do not personally prepare coffee (e.g., cashier, sanitation/maintenance). These findings suggest that the practicality and scientific basis of the recommended OELs for diacetyl merit further consideration.