Fossil fuel reserves have depleted. So, renewable and sustainable energy form an important issue. Microalgae as a third generation biomass can be an alternative carbon neutral fuel source. But its fuel quality is low. Co-pyrolysis is important technique to upgrade fuel quality of microalgae. In this study, we aimed to carry out pyrolysis of polystyrene and Spirulina sp. microalgae at low temperatures (350, 400, 450 ⁰C). The plastic waste source, polystyrene (PS), was supplied as an electronic device package. Before the pyrolysis it was divided small pieces and dried in oven. The microalgae source, Spirulina (SP), was bought in powder form commercially. The experiments were done by using semi-batch reactor setup. Co-pyrolytic product yields (bio-oil, bio-char and bio-gas) were calculated. Composition of bio-oil was enlightened by using GC-MS. As a result of the analysis, it was detected aromatic compounds like styrene, toluene in the co-pyrolytic bio-oil. Besides that it was observed co-pyrolysis was increased bio-char yield while it was decreased liquid and gas product yield. For co-pyrolysis, maximum bio-char and bio-oil yield were obtained as nearly 60% by weight at 350 ⁰C and 70% by weight at 450 ⁰C respectively.