Background: In Hong Kong, there have been significant changes in suicide rates during the period 1996–2015. Aim: We aimed to assess the impact of change in suicide rates on life expectancy in Hong Kong. Method: A decomposition method was used to quantify the impact of suicide on life expectancy in Hong Kong. Results: During 1996–2003, the increase in total suicide rate made negative contributions to the increase in life expectancy in Hong Kong (−0.15 years), with incidence component and age component accounting for −0.17 years and 0.02 years, respectively. However, during 2003–2015, the decrease in the number of suicide deaths contributed to the life expectancy by 0.16 years, with the incidence component still playing a predominant role. Furthermore, the contribution mechanism of suicide varied across suicide methods and gender. Limitations: Apart from suicide, the change in life expectancy could be affected by various factors, which needs to be considered. Moreover, conclusions of the study were made at the population level rather than the individual level. Conclusion: Suicide has a non-negligible impact on life expectancy in Hong Kong. Understanding the contribution pattern of suicide and sustaining effective strategies for suicide intervention would contribute positively to improvements in Hong Kong life expectancy.