Handling songbird nestlings is often necessary to investigate a variety of basic and applied research questions, but this may also introduce observer effects that could compromise indices of reproductive success. To test for potential observer effects while measuring nestling condition in a study population of dickcissels (Spiza americana), we handled nestlings from 18 of 30 nests in Prairie, Mississippi, USA. We used generalized linear mixed models to compare nest success rate with nests that were monitored but where nestlings were not handled. Confidence intervals for nest success rates overlapped broadly for nests with handled (0.84, 95% CI = 0.57–0.95) and unhandled nestlings (0.77, 95% CI = 0.44–0.93), and a likelihood ratio test indicated the effect of treatment did not approximate the data better than a null model. We also did not find evidence of adults rejecting or abandoning handled and banded nestlings. This suggests that it is unlikely we incurred negative impacts on nest success when measuring nestling condition in our study. © 2014 The Wildlife Society.