Esophageal squamous cell carcinoma (ESCC) is a rare gastrointestinal tumour with high mortality. A multimodality treatment based on chemoradiotherapy followed by surgery is the standard of care in the case of non-metastatic disease; chemotherapy has historically been the gold standard in the metastatic setting. However, the rate of relapse after curative treatment is high and the prognosis of ESCC is poor. In this context, immunotherapy is a novel and intriguing chance to improve survival. Therefore, in this narrative review, we depict the current scenario in the field of immunotherapy for ESCC according to the stage of disease and alongside the discussion of promising biomarkers and future perspectives. The Checkmate-577 trial showed that nivolumab is the best option as adjuvant treatment in patients with non-metastatic ESCC and residual disease after a multimodality approach. In the metastatic setting, nivolumab, pembrolizumab, camrelizumab, sintilimab and toripalimab improved survival outcomes as a first-line treatment in addition to chemotherapy. In the second-line, nivolumab, pembrolizumab, camrelizumab and tislelizumab showed positive results, with differences according to the subgroups, agents and study population included in the trials. Then, the finding of valid molecular biomarkers is crucial in selecting patients for immunotherapy.