Three lanthanide coordination polymers containing both nicotinate N-oxide and glutarate, {[Ln(NNO)(glu)] · 0.25H2O}∞ (Ln = Eu, 1; Ln = Gd, 2; Ln = Dy, 3; HNNO = nicotinic acid N-oxide, H2glu = glutaric acid), have been hydrothermally synthesized, which are isostructural, showing 2D layer network structures. The europium(III) species displays typical narrow fluorescent emission bands of the lanthanide ion. Magnetic determinations revealed that a weak antiferromagnetic interaction exists in the gadolinium(III) complex, while the dysprosium(III) analogue exhibits field-induced two-step magnetic relaxation, with an effective thermal barrier of 44.2 K.