Impulsive choice underlies several psychological disorders and can be assessed in laboratory rats using delay-discounting tasks, in which choice is for either one food pellet immediately or three food pellets after a delay. Choice for the smaller, immediate reinforcer is considered the impulsive choice. Lewis (LEW) and Fischer 344 (F344) rats differ in the number of impulsive choices made during this task when singly housed, with LEW choosing the impulsive option more often. Due to increasing recommendations to provide environmental enrichment as a component of animal-husbandry practices, a systematic replication of two previous studies was conducted using pair-housed LEW and F344. Delay discounting was assessed with pair-housed LEW and F344 and compared to previous data from singly housed LEW and F344 collected from the same laboratory. Results showed that differences in impulsive choice between the two strains were attenuated with pair housing. The main result driving this change appears to be an increase in impulsive choice in pair-housed F344 relative to singly housed F344.