The pups and white-cheeked gibbons share a home in the Asia habitat at the west suburban zoo.
Last week, one of the otters decided to approach one of the small apes and check things out.
Neubo, an 8-year-old male white-cheeked gibbon, didn't seem to mind the curious otter.
Brookfield Zoo staff says they're not sure if the encounters will continue, or if the novelty between the two species will wear off.