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Problem: The role of vitamin D (VD) in IVF outcome and immune parameters has not been elucidated well. Method of study: Women undergoing IVF treatment with GnRH agonist (Agonist) and progestin‐primed ovarian stimulation (PPOS) protocols were divided into VD lower (VDL, 25(OH)VD ≤20 ng/mL) and VD higher (VDH, 25(OH)VD >20 ng/mL) groups. Follicular fluid (FF) VD level, IVF outcomes, and peripheral blood immunophenotypes by flow cytometry were analyzed. Results: FF VD levels of the whole subjects were positively correlated with peripheral blood VD level (r = 0.86, P < 0.001). The number of mature oocytes and the blastocyst formation rate were significantly higher in women with VDH group as compared with those of VDL group in both Agonist and PPOS groups (P < 0.05, respectively). In women with PPOS protocol, peripheral blood NK and B‐cell proportions and T helper/T cytotoxic (Th/Tc) cell ratios of VDL group were significantly higher than those of VDH group (P < 0.05, respectively). In women with Agonist protocol, peripheral blood B‐cell proportion and Th/Tc ratios of VDL group were significantly higher than those of VDH group (P < 0.05, respectively). Conclusion: VD level is associated with IVF outcomes possibly derived by T‐cell immunity, particularly Th/Tc ratios. [ABSTRACT FROM AUTHOR]