Abstract We present quantitative investigations of the energy conversion pathways—electromagnetic ϵEM $left({ {epsilon} }^{EM}right)$, fluid flow ϵf $left({ {epsilon} }^{f}right)$, and particle thermal ϵth $left({ {epsilon} }^{th}right)$ energies—within the Kelvin‐Helmholtz instability (KHI) observed by the Magnetospheric Multiscale mission. We find that KHI mediates and facilitates bidirectional energy conversions among three types of energy by analyzing Joule (J⋅E) $(mathbf{J}cdot mathbf{E})$ and pressure‐strain −(P⋅∇)⋅u $left[-(mathbf{P}cdot nabla )cdot mathbf{u}right]$ energy conversions. On both the magnetosphere (MSP) and magnetosheath (MSH) sides, ϵth ${ {epsilon} }^{th}$ is converted into ϵf ${ {epsilon} }^{f}$, primarily driven by ion expansion. This suggests that the KHI acts as a relaxation mechanism, converting stored ϵth ${ {epsilon} }^{th}$ of compressed plasma at the magnetopause (MP) into ϵf ${ {epsilon} }^{f}$ associated with the KHI flow. Furthermore, the conversion between ϵEM ${ {epsilon} }^{EM}$ and ϵf ${ {epsilon} }^{f}$ is highly dependent on the spatial phase within the KHI structure: the MSP side converts ϵf ${ {epsilon} }^{f}$ to ϵEM ${ {epsilon} }^{EM}$, while the MSH side converts ϵEM ${ {epsilon} }^{EM}$ to ϵf ${ {epsilon} }^{f}$. This finding demonstrates that energy conversions are highly structured within the KHI.