Our previous work provided evidence that MICAL1 plays an essential role in the activation of ROS/Akt signalling and cell invasive phenotype and identified a novel link between RAB35 and MICAL1 in promoting breast cancer cell invasion.17 In the current study, our results suggest that MICAL1 exhibits its positively regulatory function on breast cancer cell proliferation via maintaining cyclin D expression through ROS‐sensitive PI3K/Akt/ERK signalling, which implicates an essential role for MICAL1 in breast cancer pathogenesis. Here, MICAL1 is linked to breast cancer.