The increasing prevalence of large research teams in contemporary science has prompted an investigation into the trends of team size in library and information science (LIS). In this study, we analysed 103,299 LIS publications written by 129,560 unique authors between 2000 and 2020 sourced from the Microsoft Academic Graph (MAG) data sets. We conducted a temporal analysis from multiple dimensions, including journal quartiles, research topics and researchers with varying impact levels. In addition, we employed two multivariate linear regression models – with and without author fixed effects – to scrutinise the relationship between team size and publication impact. Our findings reveal continuous growth in LIS team size. Notably, publications in higher-quartile journals tend to have larger teams; the team size of technical topic publications is generally larger than that of theoretical topic publications; and researchers with a higher h-index are able to assemble larger teams. Although we observed that co-authored papers have a higher average citation impact than single-authored papers, the overall positive impact of team expansion on citation growth is not always significant within the common LIS team size range (three to six authors). Our research suggests that indiscriminately increasing the size of a team may not be a prudent decision.