Aim To evaluate the in vitro cytotoxicity and cytokine release of three fresh root canal sealers and to determine the type of cell death they induce. Methodology The sealers tested were Sealer 26 (S26), AH Plus (AHP), and Endosequence BC Sealer (END). Fresh sealers were cultivated in contact with monocytes and polymorphonuclears (PMNs) obtained from the peripheral blood of humans. Cell viability, apoptosis and necrosis were analysed at 4 h (PMNs) or 24 h (monocytes) using Annexin‐V and propidium iodide in a cytometer. The supernatants were used to quantify Interleukin (IL)‐4, IL‐6, IL‐10, IL‐12 and tumour necrosis factor‐α (TNF‐α) in monocytes and IL‐8 in PMNs by ELISA. One‐way ANOVA and the Tukey post‐test were used to compare data for cytotoxicity, and the multiple T‐test was used to determine the differences between sealers in the release of cytokines that were statistically significant. Results After 4 h of treatment, S26 was associated with greater cell viability than the other sealers (P < 0.05) in the PMN culture and had similar values of necrosis as END (P > 0.05). After 24 h of treatment, AHP and END had greater monocyte cell viability than S26 (P < 0.05), which had more necrosis (P < 0.05). END had the lowest levels of IL‐12 compared to the other sealers (P < 0.05) and higher levels of IL‐6 compared to S26 (P < 0.05). The tested sealers did not differ in the release of IL‐8, IL‐10, TNF‐α and IL‐4 (P > 0.05). Conclusions The effect of toxic agents released varied depending on the cell type studied. The composition of the sealers appeared to alter the form of self‐regulation in the production of these cytokines by cells.