A new Gd3+ coordination polymer (CP), namely, poly[diaqua[μ4‐1′‐carboxy‐3,3′‐(diazene‐1,2‐diyl)dibenzene‐1,2,2′‐tricarboxylato]gadolinium(III)], [Gd(C16H7N2O8)(H2O)2]n, (I), has been synthesized hydrothermally from Gd(NO3)3·6H2O and azobenzene‐2,2′,3,3′‐tetracarboxylic acid (H4abtc). The target solid has been characterized by single‐crystal and powder X‐ray diffraction, elemental analysis, IR spectroscopy and susceptibility measurements. CP (I) crystallizes in the monoclinic space group C2/c. The structure features a 4‐connected topology in which Gd3+ ions are connected by carboxylate groups into a linear chain along the monoclinic symmetry direction. Adjacent one‐dimensional aggregates are bridged by Habtc3− ligands to form a two‐dimensional CP in the (10) plane. A very short hydrogen bond [O...O = 2.4393 (4) Å] links neighbouring layers into a three‐dimensional network. A magnetic study revealed antiferromagnetic Gd...Gd coupling within the chain direction. CP (I) displays a significant magnetocaloric effect (MCE), with a maximum −ΔSm of 27.26 J kg−1 K−1 for ΔH = 7 T at 3.0 K. As the MCE in (I) exceeds that of the commercial magnetic refrigerant GGG (Gd3Ga5O12, −ΔSm = 24 J kg−1 K−1, ΔH = 30 kG), CP (I) can be regarded as a potential cryogenic material for low‐temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]