Background: Screening for cancer-related psychosocial distress is an integral yet laborious component of quality oncologic care. Automated preappointment screening through online patient portals (Portal, MyChart) is efficient compared with paper-based screening, but unstudied. We hypothesized that patient access to and engagement with EHR-based screening would positively correlate with factors associated with digital literacy (eg, age, socioeconomic status). Methods: Screening-eligible oncology patients seen at our Comprehensive Cancer Center from 2014 through 2019 were identified. Patients with active Portals were offered distress screening. Portal and screening participation were analyzed via multivariable logistic regression. Household income in US dollars and educational attainment were estimated utilizing zip code and census data. Results: Of 17,982 patients, 10,279 (57%) had active Portals and were offered distress screening. On multivariable analysis, older age (odds ratio [OR], 0.97/year; P<.001); male gender (OR, 0.89; P<.001); Black (OR, 0.47; P<.001), Hawaiian/Pacific Islander (OR, 1.54; P=.007), and Native American/Alaskan Native race (OR, 0.67; P=.04); Hispanic ethnicity (OR, 0.76; P<.001); and Medicare (OR, 0.59; P<.001), Veteranâs Affairs/military (OR, 0.09; P<.01), Medicaid (OR, 0.34; P<.001), or no insurance coverage (OR, 0.57; P<.001) were independently associated with lower odds of being offered distress screening; increasing income (OR, 1.05/$10,000; P<.001) and educational attainment (OR, 1.03/percent likelihood of bachelorâs degree or higher; P<.001) were independently associated with higher odds. In patients offered electronic screening, participation rate was 36.6% (n=3,758). Higher educational attainment (OR, 1.01; P=.03) was independently associated with participation, whereas Black race (OR, 0.58; P=.004), Hispanic ethnicity (OR, 0.68; P=.01), non-English primary language (OR, 0.67; P=.03), and Medicaid insurance (OR, 0.78; P<.001) were independently associated with nonparticipation. Conclusions: Electronic portalâbased screening for cancer-related psychosocial distress leads to underscreening of vulnerable populations. At institutions using electronic distress screening workflows, supplemental screening for patients unable or unwilling to engage with electronic screening is recommended to ensure efficient yet equal-opportunity distress screening.