Background:The coronavirus disease 2019 (COVID-19) pandemic impacted global mental health, especially in young adults.Objective: This study assessed the psychological impact COVID-19 had on mental health (i.e., PTSD, anxiety, fear) in young adults ages 18 to 28 and demographic differences in this population.Methods: Data were collected between September 2020 and January 2021 through an online survey. The survey used various questionnaires to collect information that included demographics, COVID-19-related questions (quarantine status, hospitalization history, diagnosis), depression (the 9-item Patient Health Questionnaire (PHQ-9)), anxiety (the 7-item Generalized Anxiety Disorder (GAD-7)), stress from the pandemic (Impact of Events Scale-Revised (IES-R)), and the Fear of COVID-19 Scale . 183 responses were validated by inclusion/exclusion criteria. All statistical analyses were set at alpha=0.05.Results: Over 70% of participants (n=129) had at least mild anxiety, nearly 80% of participants (n=136) had at least mild depression, almost 40% (n=61) met criteria for post-traumatic stress disorder (PTSD) from the pandemic, and nearly 50% (n=88) had a high level of fear of COVID-19. Females had higher anxiety scores (t(173)=-3.352, p<.001), depression (t(166)=-3.310, p=.001), and trauma from COVID-19 ((t(151)=-2.004, p=.047) compared to males. Those who identified Hispanic/Latino/a/x had higher depression (F(2,156)=7.761, p<.001) and IES-R scores (F(2,143)=3.999, p=.020). We found that age in 2020 was associated with IES-R total scores F(1,154)=4.230, p=0.041, R2=0.027, adjusted R2=0.2. Those who were mandated a quarantine had lower anxiety (F(2,175)=3.442, p=.034) and depression (F(2,170)=3.092, p=.048) scores than those not mandated. Those who had someone close to them mandated a quarantine had lower anxiety (t(162.184)=2.705, p=.008) and IES-R scores (t(149)=2.169; p=.032) than those not mandated. Those who had someone close to them hospitalized due to a COVID-19 infection had lower anxiety scores (t(127)=2.855, p=.005), depression scores (t(123)=3.111, p=.002), and IES-R scores (t(152)=-1.975, p=.050) than those who did not have someone close to them hospitalized.Conclusions: Overall, we found significant mental health findings with various demographic differences that need further investigation and consideration. Furthermore, we found evidence suggesting the impact of an individual's social circle on a person's health during the pandemic. We recommend continued efforts to identify risk factors in vulnerable populations from the pandemic, especially in mental health, and significant public health measures to protect these populations in the future.