Recent studies have found an association between a variant in triggering receptor expressed on myeloid cells 2 (TREM2) (rs75932628-T) and both Alzheimer’s disease (AD) and cognitive function in individuals aged 80-100 years. The role of TREM2 in younger, asymptomatic individuals is unknown. We examined this variant in 1148 participants from the Wisconsin Registry for Alzheimer’s Prevention, a longitudinal study of middle-aged adults enriched for a parental history of AD. Thirteen individuals carried the T risk allele. Carriers were more likely to have a parental history of AD (100% of carriers vs. 70% of noncarriers; p = 0.01) and, among the parental history subset, families with a TREM2 carrier had a younger maternal age of AD onset than noncarriers (67.9 vs. 75.6 years; p = 0.03). There was no significant association between TREM2 carrier status and cognitive function or decline. In conclusion, the association between TREM2 and both parental history of AD and younger maternal age of AD onset provide additional support for the role of TREM2 in AD and illustrate the importance of considering family history in AD study design.