The present study aims to investigate the prevalence of loneliness and its associated factors among older adults during the COVID-19 pandemic in Bangladesh. This cross-sectional study was conducted in October 2020 among 1032 older Bangladeshi adults aged 60 years and above through telephone interviews. A semi-structured questionnaire was used to collect information on participants’ characteristics and COVID-19-related information. Meanwhile, the level of loneliness was measured using a 3-item UCLA Loneliness scale. More than half (51.5%) of the older adults experienced loneliness. We found that participants formally schooled [adjusted odds ratio (aOR = 0.62, 95% CI 0.43–0.88)] and received COVID-19-related information from health workers (aOR = 0.33, 95% CI 0.22–0.49) had lower odds of being lonely during the pandemic. However, older adults living alone (aOR: 2.57, 95% CI 1.34–4.94), residing distant from a health facility (aOR = 1.46, 95% CI 1.02–2.08) and in rural areas (aOR = 1.53, 95% CI 1.02–2.23) had higher odds of loneliness than their counterparts. Likewise, odds of loneliness were higher among those overwhelmed by COVID-19 (aOR = 1.93, 95% CI 1.29–2.86), who faced difficulty in earning (aOR = 1.77, 95% CI 1.18–2.67) and receiving routine medical care during pandemic (aOR = 2.94, 95% CI 1.78–4.87), and those perceiving requiring additional care during the pandemic (aOR = 6.01, 95% CI 3.80–9.49). The findings suggest that policies and plans should be directed to reduce loneliness among older adults who require additional care.