Display omitted •Harvesting Chlorella vulgaris using a cooking oil-CTAB emulsion was studied.•Over 90% harvesting efficiency (HE) was achieved at pH 10 and 12.•HE ˃ 90% required 0.13–0.33% (v/v) cooking oil and 2.7–6.7 mg/L CTAB.•Observed harvesting mechanisms were flocculation/sedimentation and flotation.•Proteins increased the consumption of cooking oil-CTAB emulsion by up to 6 times. In this study, a novel harvesting emulsion (HEM) consisting of cooking oil in an aqueous solution of cetyltrimethylammonium bromide (CTAB) was tested for the harvesting of a technologically important microalga, Chlorella vulgaris. The influence of HEM dose, biomass and bovine serum albumin (BSA) (model interferer compound) on harvesting efficiency (E) were studied. The HEM E was over 90% at pH 10 (0.33% (v/v) cooking oil, 6.7 mg/L of CTAB) and 12 (0.13% (v/v) cooking oil, 2.7 mg/L of CTAB). Harvesting efficiencies at pH 4 and 7 were < 73.5% due to the absence of precipitate formation. Bovine serum albumin (10 mg/L) increased the HEM dose necessary to achieve E ˃ 90% by 1.2 (pH 10), and 3 fold (pH 12). By manipulating the dose of HEM and pH, the method of harvesting (flocculation/sedimentation or flotation) was adjustable depending on the technological requirements.