The COVID-19 pandemic significantly changed mobility patterns in the Bogotá and Buenos Aires metropolitan areas, as shown by the differences between the October 2019, 2020, and 2021 indicator values derived from call detail record-based origin-destination matrices. The differences between 2019 and 2020 were more notable than between 2019 and 2021 on most mobility indicators, demonstrating a reversal of the pre-pandemic mobility habits. However, by late 2021, the return to pre-pandemic levels was still very partial in the case of public transport use (especially so in Buenos Aires), while in Bogotá the pandemic appeared to have induced a permanent-and increasing-shift to nonmotorized modes. Other mobility indicators that appear to have changed more permanently in Bogotá include the lower average distances traveled and the relatively higher importance of non-home-based mobility. In the Buenos Aires Metropolitan Area, the key persistent changes include the lower overall trip generation rates and specifically peak-hour travel, and the higher relative weight of travel to work and school compared to other travel purposes. These findings are partly explained by the underlying policy and regulatory context in the two cities and are relevant for designing transport policy in the post-pandemic context, including in terms of public transport route and schedule planning, cycleway network expansion, and, more broadly, the leveraging of big data as a complement to traditional mobility surveys.