Backgrounds: Malignant pleural mesothelioma (MPM) is a cancer with poor prognosis. Second-line and onward therapy has many options, including immune-checkpoint inhibitors with demonstrated efficacy: 10−25% objective response rate (ORR) and 40−70% disease-control rate (DCR) in clinical trials on selected patients. This study evaluated real-life 2L+ nivolumab efficacy in MPM patients and looked for factors predictive of response. Methods: This retrospective study included (September 2017−July 2021) all MPM patients managed in 11 French centers. Results: The 109 enrolled patients’ characteristics were: median age: 69 years; 67.9% men; 82.6% epithelioid subtype. Strictly, second-line nivolumab was given to 51.4%. Median PFS and OS were 3.8 (3.2−5.9) and 12.8 (9.2−16.4) months. ORR was 17/109 (15.6%); 34/109 patients had a stabilized disease (DCR 46.8%). Univariable analysis identified several parameters as significantly (p < 0.05) prognostic of OS [HR (95% CI)]: biphasic subtype: 3.3 (1.52−7.0), intermediate Lung Immune Prognostic Index score: 0.46 (0.22−0.99), progression on the line preceding nivolumab: 2.1 (1.11−3.9) and age > 70 years: 2.5 (1.5−4.0). Multivariable analyses retained only biphasic subtype: 3.57 (1.08−11.8) and albumin < 25 g/L: 10.28 (1.5−70.7) as significant and independent predictors. Conclusions: Second-line and onward nivolumab is effective against MPM in real life but with less effectiveness in >70 years. Ancillary studies are needed to identify the predictive factors.