Immunotherapy has transformed lung cancer care in recent years. In addition to providing durable responses and prolonged survival outcomes for a subset of patients with heavily pretreated non-small cell lung cancer (NSCLC), immune checkpoint inhibitors (ICIs)- either as monotherapy or in combination with other ICIs or chemotherapy-have demonstrated benefits in first-line therapy for advanced disease, the neoadjuvant and adjuvant settings, as well as in additional thoracic malignancies such as small-cell lung cancer (SCLC) and mesothelioma. Challenging questions remain, however, on topics including therapy selection, appropriate biomarker-based identification of patients who may derive benefit, the use of immunotherapy in special populations such as people with autoimmune disorders, and toxicity management. Patient and caregiver education and support for quality of life (QOL) is also important to attain maximal benefit with immunotherapy. To provide guidance to the oncology community on these and other important concerns, the Society for Immunotherapy of Cancer (SITC) convened a multidisciplinary panel of experts to develop a clinical practice guideline (CPG). This CPG represents an update to SITC's 2018 publication on immunotherapy for the treatment of NSCLC, and is expanded to include recommendations on SCLC and mesothelioma. The Expert Panel drew on the published literature as well as their clinical experience to develop recommendations for healthcare professionals on these important aspects of immunotherapeutic treatment for lung cancer and mesothelioma, including diagnostic testing, treatment planning, immune-related adverse events, and patient QOL considerations. The evidence- and consensus-based recommendations in this CPG are intended to give guidance to cancer care providers using immunotherapy to treat patients with lung cancer or mesothelioma., Competing Interests: Competing interests: CA—Consulting fees: AstraZeneca, Celgene, Eli Lilly, Genetech, Merck. SJA—Advisory board: Bristol Myers Squibb, Celsius, Merck, Samyang Biopharma, AstraZeneca/Medimmune; Consultant: Bristol Myers Squibb, Celsius, Merck, Samyang Biopharma, AstraZeneca/Medimmune, CBMG, Memgen, RAPT, Venn, Achilles Therapeutics, GlaxoSmithKline, Amgen; Scientific advisory board: CBMG, Memgen, RAPT, Venn, Achilles Therapeutics, GlaxoSmithKline, Amgen. MD—Speaker bureaus: Genentech, Merck, Bristol Myers Squibb and AstraZeneca (all have been discontinued as of November 2019). SMD—Scientific advisory boards: Johnson & Johnson Scientific, T-Cure Bioscience, LungLife AI, Early Diagnostics; Contracted research: Jansen. PMF—Consulting fees: Amgen, AstraZeneca, Bristol Myers Squibb, Iteos, Novartis, Janssen; Contracted research: AstraZeneca, Bristol Myers Squibb, Kyowa, Novartis; DSMB: Polaris, Flame. EBG—Consulting fees: ABL-Bio, Boehringer Ingelheim, Bristol Myers Squibb, Dracen, EMD Serono, Eisai, GlaxoSmithKline, Merck, Novartis; Contracted research: AstraZeneca, Bristol Myers Squibb, Dynavax, EMD Serono, Eli Lilly, Genentech, Merck, Iovance Biotherapeutics, Mirati Therapeutics, Neon, Novartis. SBG—Consulting fees: AstraZeneca, Blueprint Medicine, Bristol Myers Squibb, Boehringer Ingelheim, Genentech, Sanofi Genzyme, Daiichi Sankyo, Regeneron, Takeda, Janssen; Contracted research: AstraZeneca, Boehringer Ingelheim. RG—Consulting fee: Achilles, GenePlus, Inivata, Roche. RH—Contracted research: My institution receives funds for conducting clinical trials from Bayer and TCR2 under a cooperative research and development agreement with NCI. MDH—Consulting fees: Merck, Bristol Myers Squibb, AstraZeneca, Genentech/Roche, Nektar, Syndax, Mirati, Shattuck Labs, Immunai, Blueprint Medicines, Achilles, Arcus; Contracted research: Bristol Myers Squibb; IP rights: A patent filed by his institution related to the use of tumor mutation burden to predict response to immunotherapy (PCT/US2015/062208), which has received licensing fees from PGDx; Ownership interest: Arcus, Shattuck Labs, Immunai. RSH—Consulting fees: AbbVie Pharmaceuticals, ARMO Biosciences, AstraZeneca, Bayer HealthCare Pharmaceuticals, Bolt Biotherapeutics, Bristol Myers Squibb, Candel Therapeutics, Cybrexa Therapeutics, eFFECTOR Therapeutics, Eli Lilly and Company, EMD Serono, Foundation Medicine, Genentech/Roche, Genmab, Gilead, Halozyme Therapeutics, Heat Biologic, I-Mab Biopharma, Immunocore, Infinity Pharmaceuticals, Loxo Oncology, Merck and Company; Mirati Therapeutics, Nektar, Neon Therapeutics, NextCure, Novartis, Ocean Biomedical, Oncternal Therapeutics, Pfizer, Ribbon Therapeutics, Ventana Medical Systems, Sanofi, Seattle Genetics, Shire PLC, Spectrum Pharmaceuticals, STCube Pharmaceuticals, Symphogen, Takeda, Tesaro, Tocagen, WindMIL Therapeutics, Xencor; Contracted research: AstraZeneca, Eli Lilly and Company, Genentech/Roche, Merck and Company; Board member (non-executive/independent): Immunocore Holdings Limited, Junshi Pharmaceuticals. FRH—Consulting fees: Merck, Bristol Myers Squibb, Genentech/Roche, Lilly/Loxo, Daiichi, Novartis, AstraZeneca, Boehringer Ingelheim, OncoCyte, Amgen, Sanofi/Regeneron; Contracted research through University of Colorado: Amgen, AbbVie, Biodesix, Rain Therapeutics, Aurora Oncology, Mersana; IP rights through University of Colorado: EGFR protein and EGFR Gene Copy Number as Predictive Biomarker for EGFR Therapy. MLJ—Consulting fees – all payments made to my institution: Achilles Therapeutics, Amgen, AstraZeneca, Atreca, Boehringer Ingelheim, Bristol Myers Squibb, Daiichi Sankyo, EMD Serono, G1 Therapeutics, Roche/Genentech, GlaxoSmithKline, Gritstone, Incyte, Janssen, Lilly, Merck, Mirati, Novartis, Pfizer, Sanofi-Aventis, WindMIL Therapeutics; Contracted research – all payments made to my institution: AbbVie, Adaptimmune, Amgen, Apexigen, Array Biopharma, AstraZeneca, Atreca, BeiGene, BerGenBio, Boehringer Ingelheim, Calithera, Checkpoint Therapeutics, Corvus Pharmaceuticals, CytomX, Daiichi Sankyo, Lilly, EMD Serono, Roche/Genentech, Genmab, Genocea, GlaxoSmithKline, Gritstone Oncology, Guardant Health, Hengrui Therapeutics, Immunocore, Incyte, Janssen, Jounce, Mirati, Neovia Oncology, Novartis, Pfizer, Regeneron, Sanofi, Shattuck Labs, Syndax, Takeda, Tarveda, University of Michigan, WindMIL Therapeutics, TCR2 Therapeutics, Arcus, Ribon, Rubius Therapeutics, Tmunity Therapeutics, Seven and Eight Biosciences, Foundation Medicine; Partner consulting Fees: Otsuka. DM—Consulting fees: Gilead, G1 Therapeutics, AbbVie. JWN—Grants and personal fees: Takeda (during the conduct of the study), AstraZeneca; Grants (non-financial support): Genentech/Roche, Exelixis, Jounce Therapeutics, Eli Lilly and Company, Calithera Biosciences, Amgen, Iovance Biotherapeutics, Blueprint Pharmaceuticals, Regeneron Pharmaceuticals, Natera; Grants and non-financial support: Merck, Novartis, Boehringer Ingelheim, Nektar Therapeutics, Adaptimmune, GSK, Janssen, AbbVie. JDP—Consulting fees: AstraZeneca, AbbVie, Takeda; Contracted research: Bristol Myers Squibb, Takeda, RAIN. DLR—Consulting fees: AstraZeneca, Agendia, Amgen, BMS, Cell Signaling Technology, Cepheid, Danaher, Daiichi Sankyo, Genoptix/Novartis, GSK, Konica Minolta, Merck, NanoString, PAIGE.AI, Perkin Elmer, Roche, Sanofi, Ventana and Ultivue; Laboratory support: Amgen, Cepheid, NavigateBP, NextCure, and Konica Minolta. SS—Gift cards: Healthcasts-Syneos, ZOOM RX Surveys, Schlesinger Group, Impact Rx; Monetary compensation: Global M3. LHS—Contracted research: Merck, Bristol Myers Squibb, Regeneron. BS—Consulting fees: Bristol Myers Squibb. SITC staff: SMW—Shares owned: Pacific Biosciences, Editas Medicine; AK, LL, CG--Nothing to disclose, (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)