"Our region is disaster-prone," Lim said at his inauguration ceremony at ASEAN's Secretariat in Jakarta.
"This underscores the need to strengthen ASEAN cooperation in disaster management and humanitarian assistance," he stressed.
Earlier, the group focused mainly on regional diplomacy and economic growth.
Now it is time for the group to be more proactive and improve its capability in disaster-relief efforts, Lim stated.
Member states have to be responsible for strengthening resilience through disaster risk reduction interventions, climate change adaptation strategies and conservation and sustainable management of biodiversity and natural resources, he added.
Last month, tropical storm Tembin battered the southern Philippines, leaving at least 240 dead and tens of thousands displaced.
Also in the month, typhoon Cempaka pounded Indonesia's main island of Java and killed at least 41 people, with tens of thousands forced from their homes by severe flooding and landslides.
The ASEAN secretary-general serves a non-renewed term of five years with the post rotating among member states.
Lim takes over from Vietnam's Le Luong Minh whose working tenure ended on December 31, 2017.
