The purpose of this study was to analyse and to identify the types and abundance of microalgae across various sub-habitats (water column, sediment, rocky substrates, and mangrove roots) and to assess the environmental parameters affecting microalgae abundance in the coastal areas of Malang Regency, East Java. The research was conducted at six sites located in Malang Regency, specifically in the coastal areas of Tambakrejo, Gajahrejo, and Sitiarjo villages. A descriptive quantitative method was used. The results revealed that the microalgae identified belonged to Bacillariophyceae, Chlorophyceae, Cyanophyceae, Chrysophyceae, Dinophyceae, and Zygnematophyceae taxa. Bacillariophyceae dominated the microalgae community in the coastal area. The diversity and evenness indices indicated moderate levels, whereas the dominance index was low. Environmental variables were generally favourable for microalgae growth. NMDS statistical analysis showed significant variation in microalgae distribution across the study locations, highlighting distinct microalgae compositions at each site. Canonical correspondence analysis revealed that Bacillariophyceae were present at all sites due to their high adaptability.