Background: Despite recent advances in cancer precision medicine, patients from underserved communities do not have equal access to biomarker testing and targeted therapies. This study used a mixed-methods approach to identify barriers to equitable precision medicine access among underserved patients with non-small cell lung cancer (NSCLC). Methods: Paired national surveys (one clinician-facing and one patient-facing) were developed respectively by the Association of Community Cancer Centers (ACCC) and LUNGevity Foundation. Administered online in spring/summer 2020, the surveys were designed to identify key attitudes/barriers related to biomarker testing, resource needs, and current practice patterns for pertinent stakeholders. Survey data was triangulated with data from focus groups (2 clinician and 6 patient) conducted in fall 2020. The study was approved by Advarra IRB. Results: A total of 99 clinicians responded, with 67% (66/99) representing oncologists from community cancer programs. 248 patients responded to the LUNGevity survey, with 161 coming from the general population and 87 from the LUNGevity network (patients with relatively high income and education levels). Most clinicians surveyed indicated they were “very” (34%) or “extremely” likely (44%) to discuss biomarker testing with NSCLC patients. Academic clinicians, however, were more likely than community-based clinicians to order testing at the time of initial biopsy (76% vs 52%, P =.02). Academic clinicians were also more likely to involve the patient’s family in biomarker testing discussions (85% vs 59%, P =.009). Patient survey results identified that medical oncologists are the primary source of biomarker testing information; 64% of LUNGevity-connected and 37% of underserved patients. Eighty-five percent of LUNGevity-connected patients receive biomarker testing versus 52% for general patients (p < 0.05). Notably, more than a quarter (27%) of underserved patients who have undergone biomarker testing do not know their results. Clinician focus group participants corroborated survey findings that most clinicians receive testing results in 7-14 days, but for 23% of community and 6% of academic clinicians the process can take over 2 weeks. They identified disparities in offering biomarker testing and results to patients with known or presumed low socioeconomic status (SES) and/or health literacy. This was supported by patient survey data, which showed biomarker testing was proactively offered to only 40% of low-SES patients. Conclusions: This study identifies key areas of ongoing need related to equitable biomarker testing. Quality-improvement opportunities exist to address both clinician and patient barriers to guideline-concordant biomarker testing for underserved patients with NSCLC.