Previous studies have suggested that phosphorus (P) deficiency can increase the sensitivity of microalgae to toxic trace metals, potentially due to reduced metal detoxification at low cell P quota. The existing evidence is, however, inconsistent. This study was set up to determine the combined effects of zinc (Zn) and P supplies on Zn and P bioaccumulation and growth of the green microalgae Pseudokirchneriella subcapitata. Zinc toxicity was investigated in (i) a 24 h growth rate assay with cells varying in initial cell P quota with no supplemental P during Zn exposure and in (ii) a 48 h growth assay initiated with cells at the end of a 14-days steady state culture at three P addition rates (RARs) between 0.8 and 1.6 day−1. Our data at two experimental scenarios and the prediction under various relevant scenarios suggest a weaker effect of secondary stress factor (Zn) when nutrient deficiency (first stress factor) is prevailing.