We investigated nesting behavior and terrestrial activity in a captive population of Macrochelys temminckii (Alligator Snapping Turtle) housed outdoors in semi-natural environmental conditions in Oklahoma. The nesting season lasted from 12 May to 15 June 2012, and turtles were most active between the hours 2300–0300. Nesting duration averaged 182.5 min. Over 50% of nest construction time was spent excavating the cavity, whereas covering the eggs accounted for ∼28% of the total duration. Individual females averaged 25 non-nesting emergences before successfully depositing eggs. Terrestrial activity was positively correlated with increasing average nighttime temperature. We found thermal profiles generated by temperature data loggers affixed to females useful for studying terrestrial activity during nesting.