This study focuses on the publications of Spanish universities indexed in theWeb of Science(WoS) during 2014-2016 (125,824 articles) and calculates 17 indicators withAltmetric.com. Three objectives have been established: 1) to offer a general perspective of the altmetrics in Spanish universities, 2) to determine the coverage ofAltmetric.comin the Spanish case and 3) to establish which are the most relevant altmetrics. The results show that 42% of the articles in theWoSare indexed inAltmetric.com. The indicators generated byTwitter, the digital press,FacebookandWikipediaexplain 82% of the variance. As conclusions, it is pointed out that: a) publishing in high impact journals and in areas such as Medicine and Biology helps universities to obtain better altmetrics; and b) a small number of indicators is enough to determine the altmetric impact.