In our world today, financial sustainability challenges of Private Tertiary Institutions (PTIs) reverberate far and wide due to limited resources caused by reductions in state support in funding higher education and dwindling enrolments. These situations limit mission achievements. There are many predictions of PTIs closure due to mounting deficits. Calls for government assistance are not yielding any results as increasing demographic diversity has correlated to decreasing financial support from governments. Given this phenomenon, an investigation was carried out to find and address the financial sustainability challenges of PTIs by examining the correlate of income diversification and financial sustainability as moderated by institutional profile. The investigation utilized parametric inferential statistics by relying on regression Process v3.2 by Andrew F. Hayes model 1. The investigation was carried out in 40 out of the 60 private tertiary institutions in the Greater Accra Region of Ghana. The sample were randomly sampled to answer the self-constructed questionnaires with the Cronbach Alpha of .863 for income diversification and .852 for financial sustainability.