AbstractPlanets form in disks around young stars. The planet formation process may start when the protostar and disk are still deeply embedded within their infalling envelope. However, unlike more evolved protoplanetary disks, the physical and chemical structure of these young embedded disks are still poorly constrained. We have analyzed ALMA data for ¹³CO, C¹⁸O and N₂D⁺ to constrain the temperature structure, one of the critical unknowns, in the disk around L1527. The spatial distribution of ¹³CO and C¹⁸O, together with the kinetic temperature derived from the optically thick ¹³CO emission and the non-detection of N₂D⁺, suggest that this disk is warm enough (≳ 20 K) to prevent CO freeze-out.