This is a single institution, single-arm, window of opportunity pilot trial of pembrolizumab in patients with resectable malignant pleural mesothelioma. All patients will undergo a pretreatment PET/CT scan for clinical staging and a VATS procedure to acquire pretreatment tissue. Three cycles of pembrolizumab will then be administered (200 mg IV every 21 days). A PET/CT scan will then be repeated to assess response to pembrolizumab and then surgical resection will be performed via an extended/pleurectomy decortication at least 4 weeks after the third dose of pembrolizumab. Standard adjuvant chemotherapy consisting of cisplatin and pemetrexed for 4 cycles (every 21 days) will be given starting about 6-8 weeks following surgery, after a new baseline CT scan is obtained. Restaging CT scans will be obtained to assess response after every two cycles of chemotherapy. After the completion of standard chemotherapy, optional adjuvant treatment with pembrolizumab will be given to eligible patients for 1 year post-surgery.