This is a multicenter Phase 1b, open-label study to assess safety, tolerability, preliminary efficacy, and pharmacokinetics (PK) of cabozantinib taken in combination with atezolizumab in subjects with multiple tumor types, including advanced urothelial carcinoma (UC) (including bladder, renal pelvis, ureter, urethra), renal cell carcinoma (RCC), castration-resistant prostate cancer (CRPC), non-small-cell lung cancer (NSCLC), triple negative breast cancer (TNBC), ovarian cancer (OC), endometrial cancer (EC), hepatocellular cancer (HCC), gastric cancer/gastroesophageal junction cancer/lower esophageal cancer (GC/GEJC/LEC), colorectal cancer (CRC), head and neck (H&N) cancer, and differentiated thyroid cancer (DTC). The study consists of two stages: in the Dose Escalation Stage, an appropriate recommended cabozantinib dose for the combination with standard dosing regimen of atezolizumab will be established; in the Expansion Stage, tumor-specific cohorts will be enrolled in order to further evaluate the safety and efficacy of the combination treatment in these tumor indications. Three exploratory single-agent cabozantinib (SAC) cohorts may also be enrolled with UC, NSCLC, or CRPC subjects. One exploratory single-agent atezolizumab (SAA) cohort may also be enrolled with CRPC subjects. Subjects enrolled in the SAC cohorts and SAA cohort may receive combination treatment with both cabozantinib and atezolizumab after they experience radiographic progressive disease per the Investigator per RECIST 1.1. Due to the nature of this study design, some tumor cohorts may complete enrollment earlier than others.