Methods for accurately determining pair status of male ducks during the breeding season are necessary for further understanding the roles of paired and unpaired males in waterfowl breeding populations. Previous studies assigned pair status based on behavioral observations of randomly captured and marked birds, but this method limits control over sample sizes of paired and unpaired individuals. We evaluated 8 criteria for determining breeding-pair status (i.e., paired, unpaired) of male mallards (Anas platyrhynchos) based on scenarios of capture in decoy traps during late March–early April in Prairie-Parkland Canada and central New York, USA. Of the 51 males we classified as paired across 3 study sites and years, we confirmed from repeated visual observations that 46 (90%) were indeed paired. All 36 males classified as unpaired were subsequently confirmed to be unpaired. The predicted overall probability of correctly assigning pair status to captured males was 93.7% (95% CI = 86.8–97.3%). These criteria provide an effective yet simple technique to identify pair status of male mallards captured in decoy traps and should enable more efficient use of time and logistical resources in studies requiring samples of paired and unpaired male ducks. © 2014 The Wildlife Society.