The life expectancy provides valuable information about population health. The life expectancies were evaluated in 12,039 dogs which were buried or cremated during January 2012 to March 2015. The data of dogs were collected at the eight animal cemeteries in Tokyo. The overall life expectancy of dogs was 13.7 (95% confidence interval (CI): 13.7–13.8) years. The probability of death was high in the first year of life, lowest in the fourth year, and increased exponentially after four years of age like Gompertz curve in semilog graph. The life expectancy of companion dogs in Tokyo has increased 1.67fold from 8.6 years to 13.7 years over the past three decades. Canine crossbreed life expectancy (15.1 years, 95% CI 14.9–15.3) was significantly greater than pure breed life expectancy (13.6 years, 95% CI 13.5–13.7, P<0.001). The life expectancy for male and for female dogs were 13.6 (95% CI: 13.5–13.7) and 13.5 (95% CI: 13.4–13.6) years, respectively, with no significant difference (P=0.099). In terms of the median age of death and life expectancy for major breeds, Shiba had the highest median age of death (15.8 years), life expectancy (15.5 years) and French Bulldog had the lowest median age of death (10.2 years), life expectancy (10.2 years). When considering life expectancy alone, these results suggest that the health of companion dogs in Japan has significantly improved over the past 30 years.