The crystal structure of thiourea:diethyl oxalate in 2:1 ratio is the first of its kind where the diethyl oxalate exists as a solid which otherwise is a liquid at room temperature. It crystallizes in triclinic centrosymmetric space group P-1 with the following unit cell dimensions a=7.1870(7)Å, b=7.4890(8)Å, c=8.3637(7)Å, α=63.783(7)◦, β=67.41(1)^o, γ=64.933(7)^o.The R -factor =0.0386 for 1850 Fo>4σ(Fo) and 0.0417 for all 2020 data. There is a center of inversion at the center of the C---C bond of diethyl oxalate. This system is stabilized by N---H•••S and N ---H•••O hydrogen bonds.