Plastic waste is one of the major problems affecting Indonesian oceans and waters. Plastic surface can create new pelagic habitats for microorganisms, hence it plays a great role in the distribution of toxic and non-toxic microalgae with the potential to trigger harmful algal blooms (HABs) into other areas. This study aimed to assess the presence of microalgae attached to Polypropylene (PP) and Polyethylene Terephthalate (PET) plastic food and beverage waste, as well as its relationship with water quality at Ancol Lagoon Beach, North Jakarta. Sampling was carried out by collecting plastic waste that was submerged in the water, using purposive random sampling at 3 station points. The results showed that there were 21 genera of epiplastic microalgae originating from 3 classes, namely Bacillariophyceae (17 genera), Dinophyceae (1 genus), and Cyanophyceae (3 genera). In addition, 5 had the potential to cause HABs, namely Coscinosdiscus, Thalassiosira,and Trichodesmium from the Red Tide Maker group, as well as Prorocentrum and Pseudonitzschia from the Toxin Producer group. The Pearson correlation showed that water acidity, brightness, salinity, and dissolved oxygen had a positive correlation with the abundance of epiplastic microalgae. The microalgae community that caused HABs and were found attached to plastic waste must be closely monitored. This was primarily because the waste could be carried by currents and dispersed to other areas, including Jakarta Bay and the Seribu Islands, both of which frequently experienced HABs.