Commelina lukei is found in tropical East Africa and has been recorded from southeastern Kenya, northeastern and south-central Tanzania, including the island of Zanzibar, and Madagascar. It is found primarily in coastal areas, many of them densely populated, but it also extends inland into the much more rural Taita Hills in Kenya and the western Usambara Mountains in Tanzania. In these inland areas it is sympatric with the closely related species Commelina kotschyi. Due to the relatively wide distribution of Commelina lukei, its global conservation status is considered Least Concern based on IUCN Red List guidelines. However, it is only known from a single collection in Madagascar and its conservation situation there currently cannot be determined.