In this letter, we propose an integrated sensing and communication (ISAC) assisted energy-efficient mobile edge computing (MEC). To address the performance degradation due to interference between the radar sensing and MEC, we leverage advanced intelligent reflecting surface (IRS) to improve both the performance of the radar sensing and MEC. We adopt the radar estimation information rate as a performance measure of the radar sensing and further characterize the mutual influence between computation offloading transmission in MEC and radar sensing by accounting for the assistance of IRS. An optimization problem is formulated to minimize the total energy consumption of all devices meanwhile satisfying both the radar estimation information rate requirement as well as the latency constraint for computation offloading. We propose an efficient algorithm to optimize the computing and communication resources. The simulation results demonstrate the effectiveness of our proposed scheme of IRS assisted ISAC MEC for energy minimization.