Abstract Purpose: In oropharyngeal squamous cell carcinoma (OPC), high CD8+ tumor-infiltrating lymphocyte (CD8+TIL) density confers improved prognosis. We compared neoadjuvant durvalumab (PD-L1 inhibitor) with durvalumab + tremelimumab (CTLA-4 inhibitor) in terms of impact on CD8+TIL density, safety, and efficacy in patients with OPC. Patients and Methods: Patients with newly diagnosed stage II–IVA OPC or locoregionally recurrent OPC amenable to resection were included. Patients were randomized to two cycles of durvalumab or durvalumab + tremelimumab before surgery. The primary endpoint was change between baseline and resection specimen in CD8+TIL density between arms. Secondary endpoints included safety, response rate per RECIST, major pathologic response (MPR; ≤10% viable tumor cells) rate, and patient-reported outcomes. Results: Of 28 eligible patients (14/arm), 20 (71%) had newly diagnosed OPC, and 24 (86%) were p16-positive. The posttreatment to pretreatment median CD8+TIL density ratio was 1.31 for durvalumab and 1.15 for combination treatment (P = 0.97; 95% CI: −1.07–2.28). In each group, 6 patients (43%, 95% CI: 17.66–71.14) had a response. Eight patients (29%) had a MPR at the primary tumor and/or nodal metastases. Neither baseline CD8+TIL density nor PD-L1 expression level correlated with overall response, but a trend toward greater CD8+TIL change in patients with a MPR was seen (P = 0.059; 95% CI: −0.33–3.46). Four patients (14%) had grade ≥3 adverse events. At median follow-up time of 15.79 months, all patients were alive, and one had an additional recurrence. Conclusions: Durvalumab + tremelimumab did not increase CD8+TIL density more than durvalumab alone did. The observed safety and activity support further investigation of neoadjuvant checkpoint inhibitor for OPC.