Chile and Colombia are two South American countries with political and economic similarities that, during 2019, faced strong social outbursts, which translated into massive street protests and the weakening of their governments. Using data collected in the period immediately prior to the start of this social unrest, this study seeks to establish the role played by strong‐tied social media—which are generally homogeneous, formed by close people, and with a high potential for influencing their members—in three phenomena associated with political conflict: (a) perceived political polarization, (b) affective polarization, and (c) non‐conventional political participation. To estimate this influence, information collected through surveys in Chile in 2017 and Colombia in 2018 was used within the framework of the Comparative National Elections project. In both countries, probabilistic samples were employed to do face‐to‐face interviews with samples of over 1,100 people. In both countries, the results show that the use of social media with strong ties, specifically WhatsApp, tends to be related to two of the studied phenomena: perceived political polarization and non‐conventional participation. An interaction is also observed between WhatsApp use and political ideology that amplifies the degree of perceived political polarization, affective polarization, and participation in one or both of the countries studied. We conclude by arguing that this dual phenomenon of polarization and participation can be problematic for democracy, since polarized groups (or groups that have the perception that there is ideological polarization in the political elite) tend to consider the position of the rest of the citizens to be illegitimate, thus undermining collective problem‐solving.