We demonstrate temperature-influenced increment spacing in the sagittal otoliths of juvenile Atlantic menhadenBrevoortia tyrannusreared at different temperatures and describe otolith increment patterns from wild juveniles born in different months. Tank-reared individuals completed metamorphosis a month earlier at 25°C than at ambient temperatures (10–14°C). We identified several patterns from the sectioned otoliths, including reduced time to metamorphosis, faster transition to the juvenile stage, and increased increment spacing after onset of metamorphosis for those individuals exposed to warmer temperatures. For wild individuals that could be accurately aged, mean otolith increment spacing in the zone from 70 to 80 increments increased 1–2 μm for fish born in November and December to more than 3 μm for fish born in February. The increase in increment spacing is consistent with the arrival of individuals across seasonally warming temperatures in the estuary. A discriminant analysis based on otolith increment spacing and metamorphic patterns successfully classified birth month for 59–100% (65% overall) of Atlantic menhaden spawned between November–February. This approach is being developed ultimately to identify the birth month of wild Atlantic menhaden adults in order to test for differential survival among cohorts born in different months that recruit to the fishery.