UDP- glucose: glycoprotein glucosyltransferase (UGGT) is a protein that operates as the gatekeeper for the endoplasmic reticulum (ER) quality control mechanism of glycoprotein folding. It is known that vertebrates and  Caenorhabditis  genomes harbor two  uggt  gene copies that exhibit differences in their properties.Bayesian phylogenetic inference based on 195 UGGT and UGGT-like protein sequences of an ample spectrum of eukaryotic species showed that  uggt  genes went through independent duplications in  Caenorhabditis  and vertebrates. In both lineages, the catalytic domain of the duplicated genes was subjected to a strong purifying selective pressure, while the recognition domain was subjected to episodic positive diversifying selection. Selective relaxation in the recognition domain was more pronounced in  Caenorhabditis uggt-b  than in vertebrates  uggt-2  Structural bioinformatics analysis revealed that  Caenorhabditis  UGGT-b protein lacks essential sequences proposed to be involved in the recognition of unfolded proteins. When we assayed glucosyltrasferase activity of a chimeric protein composed by  Caenorhabditis uggt-b  recognition domain fused to  S. pombe  catalytic domain expressed in yeast, no activity was detected.The present results support the conservation of the UGGT activity in the catalytic domain and a putative divergent function of the recognition domain for the UGGT2 protein in vertebrates, which would have gone through a specialization process. In  Caenorhabditis ,  uggt-b  evolved under different constraints compared to  uggt-a  which, by means of a putative neofunctionalization process, resulted in a non-redundant paralog. The non-canonical function of  uggt-b  in the worm lineage highlights the need to take precautions before generalizing gene functions in model organisms.