Odocoileus virginianus (White-tailed Deer) currently number ∼3000 on Nantucket Island. No deer were seen on the island at the beginning of the 20^th century. The historical record suggests that a single male deer was brought to the island in 1922, and that 2 female deer were brought to the island from Michigan in 1926. After the deer population had increased to several hundred, additional deer (2 male and 3 female) were brought to Nantucket from New Hampshire in 1935 and 1936. To investigate the presence of founder effect in the population on Nantucket, we obtained samples of White-tailed Deer feces or muscle tissue from Nantucket; the New England mainland (including Cape Cod, southeastern Massachusetts, and a few samples from Maine, Connecticut, and Rhode Island), Shelter Island, NY; and Ann Arbor, MI. We amplified a portion of the mitochondrial control region (D-loop), and found 3 different sequences (haplotypes) among 35 deer samples from Nantucket. Two common haplotypes were identical or nearly identical to haplotypes from Michigan. One rare haplotype was also found in deer from the mainland in Connecticut and Massachusetts. This latter haplotype was unusual in that it contained 3 tandem copies of a 75 base-pair repeat, while most White-tailed Deer have 2 copies. In contrast, we found 5 haplotypes among 26 deer from the New England mainland. Haplotype diversity on Nantucket was 0.447 (± 0.082), and nucleotide diversity (π) was 0.021 (± 0.005). Haplotype diversity on the mainland was 0.839 (± 0.029), and π was 0.046 (± 0.002). Analysis of molecular variance (AMOVA) indicated little genetic differentiation among populations on the New England mainland (ϕ_ST = 0.095, P = 0.113). However, when the population on Nantucket was included in the analysis, there was much more genetic variation among populations (ϕ_ST = 0.414, P = 0.000). Our results indicate that most deer on Nantucket originated from 2 founding females from Michigan, and a small percentage are descended from later introductions from the New England mainland.