Plant-based yogurt is being considered as a healthy alternative due to its lactose-free and cholesterol-free benefits compared to dairy yogurt. The global plant-based food market is valued at USD 14,225.3 million in 2025 and is expected to grow in the future. This study aims to develop a plant-based walnut milk yoghurt (WMY) as an alternative to dairy yogurt. WMY preparation was carried out by following the procedures of walnut milk pasteurization, cooling, culture inoculation, and the addition of sugar, pectin, emulsifier, and vanilla. Walnut milk was incubated at 38°C for 12 h. The phenolic profile of WMY attested to a total polyphenol content of 257 mg GA/100g and a total flavonoid content of 93 mg QE/100g. WMY increased the in vitro DPPH and ABTS antioxidant activity by 76.89% and 89.93% compared with commercially available animal yogurt. WMY recorded the lowest L* index and the highest a* and b* indexes, at 47.34, 13.47, and 0.19, respectively. The reference sample exhibited the highest L* index and the lowest a* and b* indexes, measuring 67.23, 11.98, and 0.05, respectively. WMY had high scores for all sensory attributes (≥8.78) compared with those for animal yoghurt. This study highlights the benefits of plant-based yoghurt and provides a scientific basis for further optimizing the formula and production process of WMY.