With rising importance of collaborative problem-solving skills (CLPS) for the new information age, the PISA 2015 assessed students' CLPS skills on a large scale. This new attempt to measure CLPS raises an issue of validity. The purpose of this research is to examine evidence for convergent validity of CLPS through investigating the relationships among CLPS, mathematical literacy, and attitude toward collaborative activities. Because the PISA framework reflects both cognitive and social aspects of CLPS, CLPS scores should have strong relationships with mathematics literacy and attitude toward collaborative activities. We analyzed the data of 5,712 students across 177 schools in the United States. The results from random-intercept models showed that the PISA 2015 possibly underestimated the social aspect of CLPS.