Introduction: This study investigates, for the first time, the effects of plasma-treated alginate hydrogels (PTH) on porcine leukocyte activity in vitro. Cold atmospheric plasma (CAP) generates reactive oxygen and nitrogen species (RONS), which can modulate immune cell behavior and may promote tissue repair.Results: Our findings demonstrate that PTH induce a controlled increase in nitrite and superoxide production in both neutrophil and monocyte cultures, particularly at higher treatment levels, without evidence of lytic cell death or significant loss of viability. PTH application resulted in a modest non-significant decrease in neutrophil metabolic activity without promoting degranulation, while monocyte metabolism remained unaffected. These results suggest that therapeutic doses of CAP elicit moderate oxidative stress capable of activating leukocytes while preserving their functional stability.Conclusions: Overall, PTH demonstrated low cytotoxicity toward host immune cells in vitro, suggesting they may be eventually employed as bioactive materials for supporting early inflammatory responses. While their potential to enhance wound healing or tissue repair remains speculative, our findings warrant further investigation for applications in both human and veterinary medicine.