This species occurs in moist montane forest. Surveys have found the species in Ethiopia in farmland (Kassa and Bekele 2008) and grassland, bushland, Acacia woodland, and wet forest (Workeneh et al. 2011), and additionally in all stages of sugar cane plantation (Takele et al. 2011).

Crocidura fumosa occurs on Mount Kenya and in the Aberdare range, Kenya. It is found at high altitudes in three isolated "islands" in the Aberdare mountain range. It has also been found in many areas in Ethiopia (Kassa and Bekele 2008, Workeneh et al. 2011, Habtamu and Bekele 2012, Datiko and Bekele 2014, Fekdu et al. 2015, Chane and Yirga 2014, Chekol et al. 2012, Girma et al. 2012, Datiko et al. 2007, Habtamu and Bekele 2008). Found in elevations from 800 m (Datiko and Bekele 2014) up to about 3,800 m asl.

Both Aberdare and Mount Kenya are classified as National Parks and C. fumosa has a reasonable degree of protection when it occurs in these area. However, the National Parks are not entirely effective in preventing forest loss. In Ethiopia the species is found in Nechisar National Park (Workeneh et al. 2011) and Chebera Churchura National Park (Datiko and Bekele 2014).