Because internal alkenes are more challenging synthetic targets than terminal alkenes, metal-catalyzed olefin trans-position (i.e., positional isomerization) approaches have emerged to afford valuable E- or Z- internal alkenes from their complementary terminal alkene feedstocks. However, the applicability of these methods has been hampered by lack of generality, commercial availability, and scalability. In this Communication, we report a nickel-catalyzed plat-form for the stereodivergent E- or Z-selective synthesis of internal alkenes at room temperature. Under the developed protocols, conjugated and non-conjugated products that contain sensitive functional groups can be obtained in high yield and isomeric purity using commercially available catalysts and reagents. Notable mechanistic discoveries include the substoichiometric addition of an aryl iodide to enhance reactivity and selectivity for the synthesis of Z-isomers and the unusual finding of a phosphonium salt to enhance E-selectivity that we hope will inspire new perspectives on how these reagents interact with nickel centers.