Highly selective semihydrogenation of alkynes to alkenes is a highly important reaction for catalytic industry. Developing non‐noble metal based catalysts with platinum group metal‐like activity and selectivity is extremely crucial yet challenging. Metastable phase catalysts provide a potential candidate to realize high activity, yet the control of selectivity remains an open question. Here, this work first reports a metastable phase core–shell: face‐centered cubic (fcc) phase Ag (10 at%) core‐metastable hexagonal closest packed (hcp) phase Ni (90 at%) shell catalyst, which represents high conversion rate, high selectivity, and remarkable universality for the semihydrogenation of phenylacetylene and its derivatives. More impressively, a turnover frequency (TOF) value of 8241.8 h−1 is achieved, much higher than those of stable phase catalysts and reported platinum group metal based catalysts. Mechanistic investigation reveals that the surface of hcp Ni becomes more oxidized due to electron transfer from hcp Ni shell to fcc Ag core, which decreases the adsorption capacity of styrene on the metastable phase Ni surface, thus preventing full hydrogenation. This work has gained crucial research significance for the design of high performance metastable phase catalysts. The core–shell design of metastable phase nickel (Ni) catalyst achieves a beyond platinum‐group metal performance with exhibiting approaching 100% conversion rate and selectivity, good stability, and a high TOF of 8241.8 h−1. The introduction of Ag core leads to electron transfer, and more oxidation states on the catalyst surface, which is conducive to H2 dissociation and phenylacetylene adsorption.