Background: Globally, non-communicable diseases (NCD) kill about 40 million people annually, with about three-quarters of the deaths occurring in low and middle-income countries. This study was carried out to determine the patterns, trends, and causes of non-communicable disease mortality in hospitals of Tanzania from 2006-2015.Methods: This retrospective study involved primary, secondary, tertiary, and specialized hospitals in Tanzania. Death statistics were extracted from inpatient department registers, death registers, and International Classification of Diseases (ICD) report forms. Variables collected were deceased’s age, sex, cause and date of death. The ICD-10 coding system was used to assign each death to its underlying cause. Data were analysed using STATA version 14. Results: A total of 247,976 deaths were reported during the 10 years (2006–2015) in 39 hospitals. Of the total deaths, 67,711 (27.3%) were due to non-communicable diseases (NCD) and injuries. Cardio-circulatory diseases (31.9%), cancers (18.6%), chronic respiratory diseases (18.4%), and injuries (17.9%) accounted for the largest proportion (86.8%) of deaths due to NCDs. The majority (57.6%) of deaths due to NCD occurred among males. Overall, the total deaths from NCDs increased by 153.3% from 4,298 in 2006 to 10,886 in 2015. The age group 15-59 years (53.4%) was the most affected category. The overall 10-year annual age-standardized mortality rate (ASMR) for all NCDs and injuries was 235.2 per 100,0000 population. It was higher for males (287.2/100,000) than for females (186.7/100,000). The annual ASMR increased from 11.9 in 2006 to 36.5 per 100,000 populations in 2015. Most of the NCD deaths occurred in the secondary (40.0%) and primary level hospitals (27.8%). There were variations in the type of non-communicable diseases by geographical distributions. Conclusions: There was a substantial increase in ASMR due to NCDs and injuries in Tanzania from 2006 to 2015. Most of the deaths due to NCD and injuries affected the productive young adult group and males. The burden caused by NCD in the most productive ages means that families, communities, and the nation at large suffer from premature deaths. The government of Tanzania must invest in early detection and timely treatment of NCDs to reduce premature deaths.