•A simple microanode-guided electroplating method has successfully fabricated a soft-magnetic ternary alloy micropillar.•The Co63Fe25Ni12 micropillar exhibits the Ms and Hc reach an excellent level at 1.4 Oe and 175 emu/g.•Nanoindentation confirms that these pillars possessed reduced Young’s modulus at 185 GPa and the hardness of 6.38 GPa.•The study of cathodic polarization offers a detailed comprehension of the Co-Fe-Ni anomalous electrodeposition mechanism. Display omitted Microanode-guided electroplating (MAGE) was performed to prepare cobalt-iron-nickel alloying micropillars. The electrolyte was prepared by fixing Fe2+ at 0.040 M and varying Co2+ in 0.040–0.100 M and Ni2+ in 0.30–0.60 M. The effect of bath composition on the compositional, mechanical, and magnetic properties of the alloying micropillars was investigated. Resulting from FE-SEM and EDS, all the micropillars demonstrated a smooth morphology but in different compositions depending on the bath composition. Through XRD analysis, the micropillars were characterized in nanocrystals of Co-Ni and Co7Fe3. After nano-indentation testing, the reduced Young’s modulus of the pillars was estimated at 103.1–185 GPa and the hardness at 5.70–6.38 GPa. Investigation of all the specimens with VSM, Co61Fe27Ni12 and Co63Fe25Ni12 displayed the notable saturation magnetization (Ms = 180 and 175 emu/g) and the lowest coercive magnetic field (Hc = 2.1 and 1.4 Oe) among them. The mechanism of anomalous Co-Fe-Ni electrodeposition is proposed.