Microspherule protein 1 (Mcrs1) is a component of the nonspecific lethal (NSL) complex and the chromatin remodeling INO80 complex, which participates in transcriptional regulation during mitosis. Here, we investigate the roles of Mcrs1 during female meiosis in mice. We demonstrate that Mcrs1 is a novel regulator of the meiotic G2/M transition and spindle assembly in mouse oocytes. Mcrs1 is present in the nucleus and associates with spindle poles and chromosomes of oocytes during meiosis I. Depletion of Mcrs1 alters HDAC2‐mediated H4K16ac, H3K4me2, and H3K9me2 levels in nonsurrounded nucleolus (NSN)‐type oocytes, and reduces CDK1 activity and cyclin B1 accumulation, leading to G2/M transition delay. Furthermore, Mcrs1 depletion results in abnormal spindle assembly due to reduced Aurora kinase (Aurka and Aurkc) and Kif2A activities, suggesting that Mcrs1 also plays a transcription‐independent role in regulation of metaphase I oocytes. Taken together, our results demonstrate that the transcription factor Mcrs1 has important roles in cell cycle regulation and spindle assembly in mouse oocyte meiosis. Synopsis Microspherule protein 1 (Mcrs1) is involved in meiotic resumption in female mice by regulating histone modifications and the maturation promotion factor (MPF) in germinal vesicle (GV)‐stage oocytes. It also interacts with Aurora kinases to regulate spindle assembly during metaphase I. Mcrs1 regulates CDK1 activity and cyclin B1 accumulation in oocyte meiosis. Mcrs1 regulates histone modifications and transcriptional activity in GV oocytes. Mcrs1 regulates meiotic spindle assembly via the Aurora kinases in oocytes. Microspherule protein 1 is involved in meiotic resumption in female mice by regulating histone modifications and the maturation promotion factor (MPF) in germinal vesicle (GV)‐stage oocytes. It also interacts with Aurora kinases to regulate spindle assembly during metaphase I.