Estimating vitamin B12 levels in milk is challenging due to its low concentration (0.5 μg per 100 mL). A selective method using magnetic molecularly imprinted polymers (MMIPs) was developed to extract vitamin B12 from milk. The synthesis process included the preparation of oleic acid-coated iron magnetite particles obtained through co-precipitation using FeCl₂ and FeCl₃ under alkaline conditions, which were further used for magnetic molecularly imprinted polymers (MMIPs) and non-imprinted polymers (MNIPs). In this study, five different MMIPs were prepared by varying ratios of template (T) and functional monomer (FM) as 2, 4, 6; FM and cross-linker (C) as 5, 10; and initiator (I) and FM as 5, 16. Among them, the combination of T:FM- 4; C:FM- 10; FM:I- 16 demonstrated the highest binding capacity (2.4±0.11 μg B12 per mg polymer) with good imprinting factor (6.48) and selectivity (84.58%). A cross-reactivity study demonstrated minimal interference from other B vitamins on B12 binding, with binding efficiencies ranging from 2.30% (B1) to 8.43% (B6). The effects of solvent type (water, acetonitrile, methanol, NaCl) and pH (4.5-7.5) on binding were studied, showing good selectivity in aqueous solutions at pH 6.5-7.0, making the MMIP suitable for vitamin B12 extraction from milk, which has a similar pH range. The MMIP was used to extract vitamin B12 from milk. For this, milk (F: 5.25 ± 0.98 %, SNF: 8.75 ± 0.13%, protein: 3.20 ± 0.16%) was spiked with vitamin B12 at 0.1, 0.3, 0.5 and 0.7 μg/mL (three trials at each concentration). Every 5 mL of spiked milk sample was incubated with 20 mg of MMIP/MNIP for 1 h with continuous shaking. The MMIPs/MNIPs were then collected using magnets and suspended in methanol/acetic acid (9:1) for 30 min with stirring. The supernatant was filtered and analyzed using RP-HPLC, resulting in a 60.18% recovery of B12.