Global university rankings influence students’ choices and higher education policies throughout the world.When rankers not only evaluate universities but also provide them with consulting, analytics, or advertising servicesrankers are vulnerable to conflicts of interestthat may potentiallydistort theirrankings. Thepaperassessesthe impact of contracting with rankers on university ranking outcomes using difference-in-differenceresearch design.The study matchesdata on the positionsof 28 Russian universities in QS World University Rankings between2016 and2021 withinformation on contracts these universities had for services from QS –a company that produces these rankings. The study estimates the effects of the conflictsof interest with two difference-in-difference models.The first model compares the difference in five-year change in rankings between QS rankings and Times Higher Education (THE) rankings across two groups of universities –those that frequently (five times or more) contracted for QS services, and those that never or seldomly contracted for QS services. The second model compares the difference in five-year change in faculty-student ratios –between scores in QS rankings, THE rankings,and scores recorded by national statistics–across the same two groups of universities. The results suggest universities with frequent QS-related contracts hadan increase of 0.75 standard deviations (~140 positions) in QS World University Rankings and anincreaseof0.9 standard deviations in reported QS faculty-student ratio scores over five years, regardless of changes in the institutional quality.The study calls for universities, governments, and prospective students to reconsider their use of global rankingswhere conflicts ofinterest may be generated by the ranker’s business activities.