Professional social networking websites are commonly used among young professionals. In light of emerging concerns regarding social networking use and emotional distress, the purpose of this study was to investigate the association between frequency of use of LinkedIn, the most commonly used professional social networking website, and depression and anxiety among young adults. In October 2014, we assessed a nationally representative sample of 1,780 U.S. young adults between the ages of 19-32 regarding frequency of LinkedIn use, depression and anxiety, and sociodemographic covariates. We measured depression and anxiety using validated Patient-Reported Outcomes Measurement Information System measures. We used bivariable and multivariable logistic regression to assess the association between LinkedIn use and depression and anxiety, while controlling for age, sex, race, relationship status, living situation, household income, education level, and overall social media use. In weighted analyses, 72% of participants did not report use of LinkedIn, 16% reported at least some use, but less than once each week, and 12% reported use at least once per week. In multivariable analyses controlling for all covariates, compared with those who did not use LinkedIn, participants using LinkedIn at least once per week had significantly greater odds of increased depression (adjusted odds ratio [AOR] = 2.10, 95% confidence interval [CI] = 1.31-3.38) and increased anxiety (AOR = 2.79, 95% CI = 1.72-4.53). LinkedIn use was significantly related to both outcomes in a dose-response manner. Future research should investigate directionality of this association and possible reasons for it.