Recent first-line randomized controlled trials (RCTs) for patients with diffuse large B-cell lymphoma (DLBCL) have shown negative results, which may be due in part to onerous eligibility criteria limiting enrollment of poor-risk patients who require immediate treatment. We conducted a Delphi-method survey with lymphoma experts in the United States to define recommendations for essential and potentially unnecessary enrollment criteria for modern first-line DLBCL RCTs aimed at increasing clinical diversity of ensuing study groups. We first tabulated enrollment criteria from 19 DLBCL RCTs spanning the rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) era to identify common eligibility criteria from prior DLBCL RCTs for inclusion in the Delphi-method survey. We tabulated 451 total eligibility criteria comprising 51 criterion categories across 19 first-line DLBCL RCTs in the R-CHOP era. We then surveyed lymphoma clinical trial experts representing 8 academic medical centers in the United States regarding essential and unnecessary eligibility criteria for modern DLBCL RCTs. Seventeen of 29 invited clinical investigators completed the round-1 questionnaire (response rate, of 58.6%), 15 of 17 round-1 participants (88.2%) completed the round-2 survey, and all round-1 participants reviewed finalized recommendations for eligibility criteria for modern first-line DLBCL RCTs. We defined consensus recommendations for 31 modernized eligibility criteria including threshold values for 10 quantitative eligibility criteria aimed at facilitating enrollment of a clinically diverse study population in first-line DLBCL RCTs designed to improve standard-of-care therapy.