Lockdowns were the major policy response to COVID-19 containment in many countries, and subsequently many people spent abnormal amounts of time at home. Research has found that housing conditions affected more peoples’ mental health during the COVID-19 crisis than prior to it, and vulnerable groups were especially affected. One group that may be particularly vulnerable is private renters in shared housing. Using a socio-economic lens, our research examined to what extent mental well-being outcomes were associated with housing conditions in shared housing under COVID-19 restrictions in Australia. Data about private renters were obtained from the Australian Rental Housing Conditions Dataset (n= 1908), collected in mid-2020 during the easing of the first lockdown restrictions. Respondents living in shared arrangements reported higher levels of worry and anxiety (8.5–13.2%) and loneliness and isolation (3.7–18.3%) compared to other household types. Binary logistic regressions showed that COVID-19-related mental and financial well-being variables were the main contributors in COVID-19-related worry/anxiety and loneliness/isolation models. Accumulated housing problems were the only housing condition measure that was significant in the worry/anxiety model. Participants who had more than two people living in a household felt 1.4 times lonelier/isolated compared to those who lived with four or more people. Males and participants who reported good mental health were less likely to feel COVID-19-related worry/anxiety and loneliness/isolation. Our analysis demonstrates the importance of measures for mental health and income during a pandemic and concludes with recommendations of support for shared housing renters during and beyond crisis events.