The regulator of telomere elongation helicase 1 (RTEL1) is involved in maintaining telomere DNA, DNA repair, and genome stability through the disassembly of D-loops and unwinding G-quadruplex structures. RTEL1 consists of a helicase domain, two tandem harmonin homology domains (HHD1 and HHD2), and a Zn²⁺ binding RING domain. The HHD1 and HHD2 domains of RTEL1, each characterized by five α-helices, play roles in protein-protein interactions. HHD1 interacts with SLX4, a tumor suppressor protein associated with endonucleases. HHD2 interacts with Telomeric repeat-containing RNAs (TERRAs), and the 32C domain of RPA. Here, we present the crystal structure of the HHD2 domain from human RTEL1. The crystal of HHD2 domain belongs to the space group P21, with unit cell parameters a = 66.05, b = 61.96, and c = 79.95 Å. The structure was refined to a resolution of 2.8 Å with R_work/R_free = 23.9/26.83%.