Background: Archival specimens collected months or years prior to starting immunotherapy are often used to identify patients for second line immune checkpoint inhibitor (ICI) treatment. PD-L1 expression and the immune microenvironment in these patients may have altered over time following multiple lines of failed standard of care (SOC) treatments. Methods: Formalin fixed paraffin embedded (FFPE) tumor samples, taken during resection performed as first line surgical treatment from a cohort of NSCLC patients (n = 18), were evaluated by Nanostring using the IO360 gene expression panel, and by immunohistochemistry (IHC) for CD3, CD8, PD-L1, CD68 and CD163. The resultant immune profiles were correlated with the clinical follow-up data for radiotherapy, SOC chemotherapy, and second line immunotherapy with the aim of understanding whether immune signatures predictive of response to ICI therapy may be identified in such samples. Results: Of the 18 cases, clinical follow-up data indicated objective response to ICI therapy for 4 patients, with the mean time from initial diagnosis to ICI treatment being 2.8 years (range: 0.4 to 8.5 years). Although pathologist PD-L1 IHC scores were not predictive of response, IHC image analysis data revealed significant increases in CD3 (2.3-fold) and CD8 (2.7-fold) T cell numbers in the responder population. In addition, although CD68+ macrophage frequencies did not differ significantly between responder and non-responder populations, reduced M2-like CD163+ macrophage/monocyte numbers were evident for responders. While the Tumor Inflammation Signature was not predictive of response, several gene expression signatures were significantly associated with response including increased abundance of CD8 T cells, cytotoxic cells, cytotoxicity, MHC class II antigen presentation and Melanoma-Associated Antigens (MAGE). Conclusions: Despite these patients having received various lines of radiotherapy and SOC chemotherapy prior to receiving immunotherapy, immune profiles associated with response to second line immunotherapy were detected in surgical first line resection samples.