The effect of COVID-19 lockdowns on ambient air pollution levels in urban south-central Chile, where outdoor air pollution primarily originates indoors from wood burning for heating, may differ from trends in cities where transportation and industrial emission sources dominate. This quasi-experimental study compared hourly fine (PM 2.5 ) and coarse (PM 10 ) particulate matter measurements from six air monitors (three beta attenuation monitors; three low-cost sensors) in commercial and low/middle-income residential areas of Temuco, Chile in 2019 and 2020. During COVID-19 lockdown, average monthly ambient PM 2.5 concentrations in a commercial and middle-income residential neighborhood of Temuco were up to 50% higher (12 to 18 μg/m 3 ) and 59% higher (22 to 35 μg/m 3 ) than 2019 levels, respectively. Conversely, PM 2.5 levels decreased by up to 52% (43 to 21 μg/m 3 ) in low-income areas. The fine fraction of PM 10 in April 2020 was 48% higher than in April 2017-2019 (50% to 74%) in a commercial area. During COVID-19 lockdown, higher outdoor PM 2.5 pollution from wood heating existed in more affluent areas of Temuco, while PM 2.5 concentrations declined among poorer households refraining from wood heating. To reduce air pollution and energy poverty in south-central Chile, affordability of clean heating fuels (e.g. electricity) should be a policy priority.